[ios] fixed password generation crash in incognito

Bug: 951437
Change-Id: Ib25d69f2dbd3ff73240bb21e50bed4291feb0404
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1563853Reviewed-by: Vadym Doroshenko <dvadym@chromium.org>
Commit-Queue: David Jean <djean@chromium.org>
Cr-Commit-Position: refs/heads/master@{#649808}

ios/chrome/browser/passwords/password_controller.mm

@@ -694,7 +694,8 @@ void LogSuggestionShown(PasswordSuggestionType type) {
 - (BOOL)canGeneratePasswordForForm:(NSString*)formName
                    fieldIdentifier:(NSString*)fieldIdentifier
                          fieldType:(NSString*)fieldType {
-  if (!features::IsAutomaticPasswordGenerationEnabled())
+  if (!features::IsAutomaticPasswordGenerationEnabled() ||
+      _passwordManagerClient->IsIncognito())
     return NO;
   if (![fieldType isEqualToString:@"password"])
     return NO;