Qt5 backend hangs after clicking the edit axis toolbar icon

Description

What steps will reproduce the problem?

1. Set Qt5 as graphics backend
2. Create a matplotlib plot; e.g. plt.plot()
3. Click “Edit axis, curve and image paramters” toolbar icon
4. Close the popup window
5. The Qt window hangs

I confirmed that this behavior manifested in bootstrap with PR #14025

Bad behavior

Commit f20053facde83c1be4a67a723109fa3f314b9cb1

Good behavior

Commit 4e15ee0e7d8d2839c2bfc51c618c94d7e0ff1216

Versions

• Spyder version: 5.3.0.dev0 861b1f274
• Python version: 3.9.7
• Qt version: 5.12.9
• PyQt5 version: 5.12.3
• Operating System: Darwin 20.6.0

Dependencies

# Mandatory:
applaunchservices >=0.1.7     :  0.2.1 (OK)
atomicwrites >=1.2.0          :  1.4.0 (OK)
chardet >=2.0.0               :  4.0.0 (OK)
cloudpickle >=0.5.0           :  2.0.0 (OK)
cookiecutter >=1.6.0          :  1.7.3 (OK)
diff_match_patch >=20181111   :  20200713 (OK)
intervaltree >=3.0.2          :  3.0.2 (OK)
IPython >=7.6.0               :  7.30.0 (OK)
jedi >=0.17.2;<0.19.0         :  0.18.1 (OK)
jellyfish >=0.7               :  0.8.9 (OK)
jsonschema >=3.2.0            :  4.2.1 (OK)
keyring >=17.0.0              :  23.4.0 (OK)
nbconvert >=4.0               :  6.3.0 (OK)
numpydoc >=0.6.0              :  1.1.0 (OK)
parso >=0.7.0;<0.9.0          :  0.8.3 (OK)
pexpect >=4.4.0               :  4.8.0 (OK)
pickleshare >=0.4             :  0.7.5 (OK)
psutil >=5.3                  :  5.8.0 (OK)
pygments >=2.0                :  2.10.0 (OK)
pylint >=2.5.0                :  2.12.1 (OK)
pyls_spyder >=0.4.0           :  0.4.0 (OK)
pylsp >=1.3.1;<1.4.0          :  1.4.0.dev0 (OK)
pylsp_black >=1.0.0           :  1.0.0 (OK)
qdarkstyle =3.0.2             :  3.0.2 (OK)
qstylizer >=0.1.10            :  0.2.1 (OK)
qtawesome >=1.0.2             :  1.1.1 (OK)
qtconsole >=5.2.1;<5.3.0      :  5.2.1 (OK)
qtpy >=1.5.0                  :  1.11.2 (OK)
rtree >=0.9.7                 :  0.9.7 (OK)
setuptools >=49.6.0           :  59.4.0 (OK)
sphinx >=0.6.6                :  4.3.1 (OK)
spyder_kernels >=2.2.0;<2.3.0 :  2.3.0.dev0 (OK)
textdistance >=4.2.0          :  4.2.2 (OK)
three_merge >=0.1.1           :  0.1.1 (OK)
watchdog >=0.10.3             :  2.1.6 (OK)
zmq >=17                      :  22.3.0 (OK)

# Optional:
cython >=0.21                 :  0.29.24 (OK)
matplotlib >=2.0.0            :  3.5.0 (OK)
numpy >=1.7                   :  1.21.4 (OK)
pandas >=1.1.1                :  1.3.4 (OK)
scipy >=0.17.0                :  1.7.3 (OK)
sympy >=0.7.3                 :  1.9 (OK)

[impact27]

I opened https://github.com/matplotlib/matplotlib/pull/22202

[impact27]

@mrclary Could you try: go to matplotlib/backends/qt_editor/_formlayout.py Locate

if qt_compat._exec(dialog):
        return dialog.get()

Replace by: dialog.show()