Fix mutating array during iteration crash (#11379)

Author: paulb777

FirebaseABTesting/CHANGELOG.md

@@ -1,3 +1,6 @@
+# 10.11.0
+- [fixed] Fix crash caused by mutating array during iteration. (#11378)
+
 # 8.2.0
 - [fixed] Fixed analyze issue introduced in Xcode 12.5. (#8209)
 

FirebaseABTesting/Sources/FIRExperimentController.m

@@ -90,7 +90,7 @@
       [ABTConditionalUserPropertyController sharedInstanceWithAnalytics:analytics];
 
   // Check if the experiment is in experiments but not payloads.
-  for (id experiment in experiments) {
+  for (id experiment in [experiments copy]) {
     BOOL doesExperimentNoLongerExist = YES;
     for (NSData *payload in payloads) {
       ABTExperimentPayload *experimentPayload = ABTDeserializeExperimentPayload(payload);