fix: don't change groups when updating an instance

Signed-off-by: flow <flowlnlnln@gmail.com>

launcher/InstanceList.cpp

@@ -913,9 +913,11 @@ bool InstanceList::commitStagedInstance(QString path, InstanceName const& instan
                 qWarning() << "Failed to move" << path << "to" << destination;
                 return false;
             }
-        }
+
             m_instanceGroupIndex[instID] = groupName;
             m_groupNameCache.insert(groupName);
+        }
+
         instanceSet.insert(instID);
 
         emit instancesChanged();