fix(span-evidence): Prevent TypeError from nullish spans in NPlusOneDBQueriesSpanEvidence

[sentry]

The NPlusOneDBQueriesSpanEvidence component was encountering a TypeError: undefined is not an object (evaluating 'e.op').

This occurred because the offendingSpans array, which is derived from evidenceData mapping to event spans, could contain null or undefined elements. This happens when evidenceData references span IDs that are no longer present in the event's full span list (e.g., due to trimming or partial payloads).

The existing guard (span.op || '') only protected against a missing op property on a valid span object, but not against span itself being null or undefined.

This fix introduces an upfront filter(Boolean) on offendingSpans to create validSpans. All subsequent operations that access span properties now use validSpans, ensuring that only valid span objects are processed and preventing the TypeError.

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Fixes JAVASCRIPT-3B3W

_{Comment @sentry <feedback> on this PR to have Autofix iterate on the changes.}