warning not being displayed the first time around when clicking on `Confirm Sync Code` without any code added

Description

When clicking on Confirm Sync Code under Enter a sync code, the entire modal will get closed without any warnings. When you open the Enter a sync code modal again, you’ll get the warning from the previous failure.

Steps to Reproduce

1. launch brave (0.59.20 Chromium: 72.0.3626.28 in this instance)
2. open brave://sync and click on I Have a Sync Code
3. click on Confirm Sync Code without adding anything into the text field
4. you’ll notice that the entire modal is closed right away without any warnings
5. click on I Have a Sync Code and you’ll receive the warning that should have appeared in the first place

Actual result:

Expected result:

Should be warning the user that the import failed rather than closing the modal and than warning the user once they go into the Enter a sync code for a second time.

Reproduces how often:

100% reproducible using the above STR.

Brave version (brave://version info)

Brave	0.59.20 Chromium: 72.0.3626.28 (Official Build) beta(64-bit)
Revision	997b1040b63bac324e815797ba52be0cd8f616ed-refs/branch-heads/3626@{#461}
OS	Mac OS X

Reproducible on current release:

• Does it reproduce on brave-browser dev/beta builds?

Reproducible on beta and assuming it’s also reproducible on dev as well as the new UI would have been merged into dev first.

[LaurenWags]

Same thing happens if you enter an invalid sync code. STR:

1. launch brave (0.59.20 Chromium: 72.0.3626.28 in this instance)
2. open brave://sync and click on I Have a Sync Code
3. enter code that is incorrect and click on Confirm Sync Code
4. you’ll notice that the entire modal is closed right away without any warnings
5. click on I Have a Sync Code and you’ll receive the warning that should have appeared in the first place

[btlechowski]

Verification passed on

Brave	0.59.26 Chromium: 72.0.3626.64 (Official Build) beta (64-bit)
Revision	eaa9668e80ce5405e7f1902579558ea725c06ca1-refs/branch-heads/3626@{#708}
OS	Windows

Used test plan from https://github.com/brave/brave-core/pull/1357 and from https://github.com/brave/brave-browser/issues/2845#issuecomment-452372326

Verification PASSED on macOS 10.14.2 using the following build:

Brave	0.59.26 Chromium: 72.0.3626.64 (Official Build) beta(64-bit)
Revision	eaa9668e80ce5405e7f1902579558ea725c06ca1-refs/branch-heads/3626@{#708}
OS	Mac OS X

Verification passed on Ubuntu 17.10

Brave	0.59.26 Chromium: 72.0.3626.64 (Official Build) beta (64-bit)
Revision	eaa9668e80ce5405e7f1902579558ea725c06ca1-refs/branch-heads/3626@{#708}
OS	Linux