Avoid exception when __frame_data["code_context"] is None

[dschult]

As part of DelayedImportErrorModule, an exception message is created for ModuleNotFound. That message creation uses __frame_data including code_context. But it raises a secondary TypeError exception if fd["code_context'] is None.

This PR handles the case of no code_context by adding or "" to get fd["code_context"] or ""
See networkx/networkx#7062

I wasn't able to make a test for this easily because I don't know how to create some code for a test with code_context showing up as None. But this change is presumably harmless at worst and hopes to reduce confusion when a moduleNotFound error is raised for a DelayedImportErrorModule.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (fbd805b) 93.95% compared to head (0ece17a) 93.95%.

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Additional details and impacted files

@@ Coverage Diff @@ ## main #83 +/- ## ======================================= Coverage 93.95% 93.95% ======================================= Files 4 4 Lines 182 182 ======================================= Hits 171 171 Misses 11 11 

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[stefanv]

Thanks @dschult!