scrapy bench fails in 2.6.1

Description

Running scrapy bench in 2.6.1 gives AttributeError exception

Steps to Reproduce

1. pip install scrapy==2.6.1 --upgrade
2. scrapy bench

Expected behavior: [What you expect to happen] It works fine in 2.5.1:

2022-03-15 20:59:25 [scrapy.core.engine] INFO: Spider closed (closespider_timeout)

Actual behavior: [What actually happens]

2022-03-15 20:57:36 [scrapy.utils.log] INFO: Scrapy 2.6.1 started (bot: scrapybot)
2022-03-15 20:57:36 [scrapy.utils.log] INFO: Versions: lxml 4.8.0.0, libxml2 2.9.12, cssselect 1.1.0, parsel 1.6.0, w3lib 1.22.0, Twisted 22.2.0, Python 3.9.7 (default, Sep 16 2021, 13:09:58) - [GCC 7.5.0], pyOpenSSL 22.0.0 (OpenSSL 1.1.1m  14 Dec 2021), cryptography 36.0.1, Platform Linux-5.10.0-12-amd64-x86_64-with-glibc2.31
2022-03-15 20:57:37 [scrapy.crawler] INFO: Overridden settings:
{'CLOSESPIDER_TIMEOUT': 10, 'LOGSTATS_INTERVAL': 1, 'LOG_LEVEL': 'INFO'}
2022-03-15 20:57:37 [scrapy.extensions.telnet] INFO: Telnet Password: cd24a9fdad5af2a4
2022-03-15 20:57:37 [scrapy.middleware] INFO: Enabled extensions:
['scrapy.extensions.corestats.CoreStats',
 'scrapy.extensions.telnet.TelnetConsole',
 'scrapy.extensions.memusage.MemoryUsage',
 'scrapy.extensions.closespider.CloseSpider',
 'scrapy.extensions.logstats.LogStats']
2022-03-15 20:57:37 [scrapy.middleware] INFO: Enabled downloader middlewares:
['scrapy.downloadermiddlewares.httpauth.HttpAuthMiddleware',
 'scrapy.downloadermiddlewares.downloadtimeout.DownloadTimeoutMiddleware',
 'scrapy.downloadermiddlewares.defaultheaders.DefaultHeadersMiddleware',
 'scrapy.downloadermiddlewares.useragent.UserAgentMiddleware',
 'scrapy.downloadermiddlewares.retry.RetryMiddleware',
 'scrapy.downloadermiddlewares.redirect.MetaRefreshMiddleware',
 'scrapy.downloadermiddlewares.httpcompression.HttpCompressionMiddleware',
 'scrapy.downloadermiddlewares.redirect.RedirectMiddleware',
 'scrapy.downloadermiddlewares.cookies.CookiesMiddleware',
 'scrapy.downloadermiddlewares.httpproxy.HttpProxyMiddleware',
 'scrapy.downloadermiddlewares.stats.DownloaderStats']
2022-03-15 20:57:37 [scrapy.middleware] INFO: Enabled spider middlewares:
['scrapy.spidermiddlewares.httperror.HttpErrorMiddleware',
 'scrapy.spidermiddlewares.offsite.OffsiteMiddleware',
 'scrapy.spidermiddlewares.referer.RefererMiddleware',
 'scrapy.spidermiddlewares.urllength.UrlLengthMiddleware',
 'scrapy.spidermiddlewares.depth.DepthMiddleware']
2022-03-15 20:57:37 [scrapy.middleware] INFO: Enabled item pipelines:
[]
2022-03-15 20:57:37 [scrapy.core.engine] INFO: Spider opened
2022-03-15 20:57:37 [scrapy.extensions.logstats] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
2022-03-15 20:57:37 [scrapy.extensions.telnet] INFO: Telnet console listening on 127.0.0.1:6023
2022-03-15 20:57:38 [scrapy.extensions.logstats] INFO: Crawled 61 pages (at 3660 pages/min), scraped 0 items (at 0 items/min)
2022-03-15 20:57:39 [scrapy.extensions.logstats] INFO: Crawled 117 pages (at 3360 pages/min), scraped 0 items (at 0 items/min)
2022-03-15 20:57:40 [scrapy.extensions.logstats] INFO: Crawled 165 pages (at 2880 pages/min), scraped 0 items (at 0 items/min)
2022-03-15 20:57:41 [scrapy.extensions.logstats] INFO: Crawled 214 pages (at 2940 pages/min), scraped 0 items (at 0 items/min)
2022-03-15 20:57:42 [scrapy.extensions.logstats] INFO: Crawled 269 pages (at 3300 pages/min), scraped 0 items (at 0 items/min)
2022-03-15 20:57:43 [scrapy.extensions.logstats] INFO: Crawled 317 pages (at 2880 pages/min), scraped 0 items (at 0 items/min)
2022-03-15 20:57:44 [scrapy.extensions.logstats] INFO: Crawled 358 pages (at 2460 pages/min), scraped 0 items (at 0 items/min)
2022-03-15 20:57:45 [scrapy.extensions.logstats] INFO: Crawled 406 pages (at 2880 pages/min), scraped 0 items (at 0 items/min)
2022-03-15 20:57:46 [scrapy.extensions.logstats] INFO: Crawled 453 pages (at 2820 pages/min), scraped 0 items (at 0 items/min)
2022-03-15 20:57:47 [scrapy.core.engine] INFO: Closing spider (closespider_timeout)
2022-03-15 20:57:47 [scrapy.extensions.logstats] INFO: Crawled 486 pages (at 1980 pages/min), scraped 0 items (at 0 items/min)
2022-03-15 20:57:48 [scrapy.statscollectors] INFO: Dumping Scrapy stats:
{'downloader/request_bytes': 215773,
 'downloader/request_count': 501,
 'downloader/request_method_count/GET': 501,
 'downloader/response_bytes': 1458919,
 'downloader/response_count': 501,
 'downloader/response_status_count/200': 501,
 'elapsed_time_seconds': 10.63502,
 'finish_reason': 'closespider_timeout',
 'finish_time': datetime.datetime(2022, 3, 15, 19, 57, 48, 193820),
 'log_count/INFO': 20,
 'memusage/max': 62078976,
 'memusage/startup': 62078976,
 'request_depth_max': 19,
 'response_received_count': 501,
 'scheduler/dequeued': 501,
 'scheduler/dequeued/memory': 501,
 'scheduler/enqueued': 10021,
 'scheduler/enqueued/memory': 10021,
 'start_time': datetime.datetime(2022, 3, 15, 19, 57, 37, 558800)}
2022-03-15 20:57:48 [scrapy.core.engine] INFO: Spider closed (closespider_timeout)
2022-03-15 20:57:48 [scrapy.core.engine] INFO: Error while scheduling new request
Traceback (most recent call last):
  File "/home/nordange/anaconda3/envs/scraping/lib/python3.9/site-packages/twisted/internet/task.py", line 526, in _oneWorkUnit
    result = next(self._iterator)
StopIteration

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/nordange/anaconda3/envs/scraping/lib/python3.9/site-packages/twisted/internet/defer.py", line 857, in _runCallbacks
    current.result = callback(  # type: ignore[misc]
  File "/home/nordange/anaconda3/envs/scraping/lib/python3.9/site-packages/scrapy/core/engine.py", line 187, in <lambda>
    d.addBoth(lambda _: self.slot.nextcall.schedule())
AttributeError: 'NoneType' object has no attribute 'nextcall'

Reproduces how often: [What percentage of the time does it reproduce?] 100%

Versions

Scrapy       : 2.6.1
lxml         : 4.8.0.0
libxml2      : 2.9.12
cssselect    : 1.1.0
parsel       : 1.6.0
w3lib        : 1.22.0
Twisted      : 22.2.0
Python       : 3.9.7 (default, Sep 16 2021, 13:09:58) - [GCC 7.5.0]
pyOpenSSL    : 22.0.0 (OpenSSL 1.1.1m  14 Dec 2021)
cryptography : 36.0.1
Platform     : Linux-5.10.0-12-amd64-x86_64-with-glibc2.31

[Laerte]

@Gallaecio I tested locally

• #5440

Fixes the issue.

[Gallaecio]

Soon™