File Icons Disappear Randomly

NOTE: I am currently looking into this, but I'm just keeping this here for future reference.

Given enough time, when the tree view is updated or the window is refocused, the icons for both the main tree view and the details pane on the bottom (and at times, the icon in the address bar) disappear. Selecting a different item in the tree view does seem to bring the icon back only for the details panel.

I do not know why this happens, but I do know it only started occurring after asynchronous file loading was implemented (specifically in commit b0bfc760), which leaves me to believe it has something to do with the QIcon being loaded in the worker thread.

I do plan to rework the file loading thread, but I don't actually know why it affects the details pane and address bar as well.