fix(ios): Resolve fetchViewHierarchy with nil on capture failure

When `captureViewHierarchy` returned nil the ObjC code still constructed
an empty `NSMutableArray` and resolved with it. In JS, `[]` is truthy —
the caller would treat the failure as a successful (empty) attachment.
Bail out with `resolve(nil)` up front so the JS side sees the actual
failure signal.

Pre-existing since 2023; flagged by Seer while reviewing this PR.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: alwx

packages/core/ios/RNSentry.mm

@@ -683,6 +683,12 @@ - (void)handleShakeDetected
 {
 #if TARGET_OS_IPHONE || TARGET_OS_MACCATALYST
     NSData *rawViewHierarchy = [RNSentryInternal captureViewHierarchy];
+    if (rawViewHierarchy == nil) {
+        // Propagate the capture failure to JS instead of a truthy `[]`, which
+        // would be treated as a successful (empty) attachment.
+        resolve(nil);
+        return;
+    }
 
     NSMutableArray *viewHierarchy = [NSMutableArray arrayWithCapacity:rawViewHierarchy.length];
     const char *bytes = (char *)[rawViewHierarchy bytes];