Fix the test for basic app

[greyli]

1. Update the test app

If I understand correctly, the debug toolbar will only be enabled if app.debug is True. So I added the DEBUG=True to the test app.

Related code:

flask-debugtoolbar/src/flask_debugtoolbar/__init__.py

Line 114 in 2b8bf9c

'DEBUG_TB_ENABLED': app.debug,

2. Update the src/flask_debugtoolbar/__init__.py

Fix the two if statements to prevent the following errors:

>       if 'gzip' in response.headers.get('Content-Encoding'):
E       TypeError: argument of type 'NoneType' is not iterable

Since the response.headers.get('Content-Encoding') could be None.

With this PR, all the tests will be passed. The failed style checker will be fixed in #219

[macnewbold]

This looks great, and looks like it's passing the automated tests other than stylecheck. If we can get that one passing, I'm 100% on board with merging this. If we can't and there's a good reason to merge it with that failing, I'm open minded to that too.

[jeffwidman]

Everything looks good to me except I don't understand the rationale for the removal of TESTING=True.

[jeffwidman]

I thought it was best practice to set this when in tests?

Looks like that's still true for Flask 3.0.x: https://flask.palletsprojects.com/en/3.0.x/testing/

I realize the main side-effect of propagating exceptions also happens when DEBUG is True, but still seems best to follow best practices as later on additional side effects may be added.

Overall, the presence/absence of this seems like it shouldn't affect whether the tests pass/fail which is the purpose of this PR, so IMO I'd extract this change to a separate PR.

[greyli]

Thanks for the review. I guess I made a mistake here. I don't need to remove this line, but just add the debug = True line. Updated.

[jeffwidman]

I just merged #219 and rebased this, nice to see everything 🟢 !

[jeffwidman]

Awesome thanks so much for this!

[jeffwidman]

Now that these checks are all passing, I went ahead and enabled them all as required checks against master.

I have zero objections if for some reason another maintainer needs to temporarily override these and merge a PR, but obviously use your judgement as that should probably be the exception rather than the rule now that folks have gone to so much effort to bring us up to date.

cc @macnewbold @nickjj @greyli