To explain this bug I'll take the support forums as example. Once we've solved the issue we change the topic so that it holds a topic icon, if the original user edits the post after the team member set the topic icon the topic icon set by the team member will be lost.
This is due to the request_var call used to get the topic icon which will set the default value to 0. The following patch will make it so that the topic icon will stick in this case.