Fix 21918 - Segfault for getParameterStorageClasses for invalid funct…

[MoonlightSentinel]

…ions

The type of a FuncDeclaration is set to TypeError if the auto
inference fails. So getParameters has to check that the type is
actually a TypeFunction.

The additional check in traits.d prevents the invalid error message:

Error: parameter index must be in range 0..0 not 0

[dlang-bot]

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	21918	minor	segfault in getParameterStorageClasses on auto function with error

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "stable + dmd#12517"

[12345swordy]

Tests?

[MoonlightSentinel]

Forgot to stage the test case 😅