ignore tap on legacy non-blocking SN change message

// FREEBIE

Signal/src/ViewControllers/ConversationView/MessagesViewController.m

@@ -2396,9 +2396,13 @@ typedef enum : NSUInteger {
     DDLogWarn(@"%@ Unhandled tap for error message:%@", self.tag, message);
 }
 
-- (void)tappedNonBlockingIdentityChangeForRecipientId:(NSString *)signalId
+- (void)tappedNonBlockingIdentityChangeForRecipientId:(nullable NSString *)signalId
 {
-    NSParameterAssert(signalId != nil);
+    if (signalId == nil) {
+        // Before 2.13 we didn't track the recipient id in the identity change error.
+        DDLogWarn(@"%@ Ignoring tap on legacy nonblocking identity change since it has no signal id", self.tag);
+        return;
+    }
 
     [self showFingerprintWithRecipientId:signalId];
 }