fix(logs): Allow null custom attributes without debug warning

[limbonaut]

Passing null as custom attributes to log functions prints a spurious debug message ("Discarded custom attributes on log: non-object sentry_value_t passed in"). Null is a valid way to indicate "no custom attributes" — the metrics path in construct_metric() already handles this correctly.

Came up while working on sentry-godot metrics support. The Godot SDK has a shared dictionary_to_attributes() helper used by both logs and metrics. Ideally it returns null for empty dictionaries to avoid an unnecessary allocation, but the log path warned about it.

[jpnurmi]

Thanks! Looks like a miss. Even the docs suggest passing sentry_value_new_null().

sentry-native/include/sentry.h

Line 2203 in 923427f

* You can pass `sentry_value_new_null()` to logs which don't need attributes.

[limbonaut]

Refactored to use switch statement for clarity.

[jpnurmi]

Refactored to use switch statement for clarity.

Not sure why/how/where the flag comes from, but the Windows ClangCL configuration builds with -Wswitch-enum:

D:\a\sentry-native\sentry-native\src\sentry_logs.c(256,21): error : 7 enumeration values not explicitly handled in switch: 'SENTRY_VALUE_TYPE_BOOL', 'SENTRY_VALUE_TYPE_INT32', 'SENTRY_VALUE_TYPE_INT64'... [-Werror,-Wswitch-enum] [C:\Users\runneradmin\AppData\Local\Temp\pytest-of-runneradmin\pytest-0\cmake0\sentry.vcxproj]

[limbonaut]

I see, hmm. Looks like it wants all flags to be explicitly handled? default doesn't cut it. I rolled back to if-statements.

[limbonaut]

Found this: llvm/llvm-project#148856

[jpnurmi]

Claude suggests using /clang:-Wall instead of -Wall with clang-cl. Unlike regular clang where -Wall is a curated subset, clang-cl's -Wall means -Weverything which includes -Wswitch-enum. 😵

Edit: I was just curious, but didn't mean we'd start messing with the flags in this PR, by the way. I'm happy with the original else-if proposal.