[Radar] When opening, refresh the avatar list gui

Normally we cut back on refreshAvatarList calls to avoid work when not visible.
When we reopen, there needs to be a call to refreshAvatarList so the user isn't waiting for position updates to see correct data.

indra/newview/llfloateravatarlist.cpp

@@ -268,6 +268,7 @@ void LLFloaterAvatarList::draw()
 
 void LLFloaterAvatarList::onOpen()
 {
+	if (mAvatars.size()) refreshAvatarList();
 }
 
 void LLFloaterAvatarList::onClose(bool app_quitting)