Apply untoggle_optimizer when result is None

[deng-cy]

What does this PR do?

Fixes #5723.

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[codecov]

Codecov Report

Merging #5738 (c6b1a72) into master (2036318) will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master   #5738   +/-   ##
======================================
  Coverage      93%     93%           
======================================
  Files         134     134           
  Lines       10059   10059           
======================================
  Hits         9394    9394           
  Misses        665     665           

[carmocca]

Can you write a test that fails without the changes here?

[deng-cy]

Can you write a test that fails without the changes here?

I have some difficulty to find relevant test files. Is there any test when training_step returns None? I can start to work from there.

[carmocca]

See: https://github.com/PyTorchLightning/pytorch-lightning/blob/c6b1a7264321ca81682dc1aaa4ba21edce67c399/tests/trainer/data_flow/test_train_loop_flow_scalar_1_0.py#L207-L272

[Borda]

@deng-cy there won't be any more releases in 1.1.x so I have changed your destination branch to feat 1.2
pls, there is no need to close this PR, just rebase on the target branch, or maybe easier just cherry-pick the commit (@kaushikb11 will help you if needed)

[tchaton]

Hey @deng-cy,

Moved your commits to this PR: #5983

I applied a git reset --hard origin/master && git push -f and GitHub closed the PR :)
I didn't manage to reopen it.

I apologise for this.

Best,
T.C

[Borda]

@tchaton any reason for closing?

[kaushikb11]

@Borda #5983

[deng-cy]

Sorry I have been too busy recently to write a test case for this. Thanks for the new PR. I will look into details as soon as possible.