Crash preventation

Author: David Grigoryan

Crashlytics/Crashlytics/Controllers/FIRCLSNetworkClient.m

@@ -132,12 +132,16 @@ - (BOOL)supportsBackgroundRequests {
 
 - (void)attemptToReconnectBackgroundSessionWithCompletionBlock:(void (^)(void))completionBlock {
 if (!self.supportsBackgroundRequests) {
-completionBlock();
+if (completionBlock) {
+completionBlock();
+ }
 return;
  }
 
 // This is the absolute minimum necessary. Perhaps we can do better?
- [[NSOperationQueuemainQueue] addOperationWithBlock:completionBlock];
+if (completionBlock) {
+ [[NSOperationQueuemainQueue] addOperationWithBlock:completionBlock];
+ }
 }
 
 #pragma mark - API