Don't show leave group option if user has already left

Signal/src/ViewControllers/ThreadSettings/OWSConversationSettingsViewController.m

@@ -683,6 +683,8 @@ const CGFloat kIconViewLength = 24;
                 [weakSelf showGroupMembersView];
             }]
         ];
+        NSString *userPublicKey = OWSIdentityManager.sharedManager.identityKeyPair.hexEncodedPublicKey;
+        if ([((TSGroupThread *)self.thread).groupModel.groupMemberIds containsObject:userPublicKey]) {
             [mainSection addItem:[OWSTableItem
                 itemWithCustomCellBlock:^{
                     UITableViewCell *cell =
@@ -700,6 +702,7 @@ const CGFloat kIconViewLength = 24;
                 }]
             ];
         }
+    }
     
 
     // Mute thread section.