Custom icons suppress subtree UI hint

In the left sidebar, when a collection or document has a custom icon and subdocuments, and is in a collapsed state, there is no UI indication about the presence of collapsed subdocuments until the mouse hovers over the title.

This is not an issue without custom icons, as in that case the triangle that indicates the presence of subdocuments is always displayed.

This makes it so that when you have many documents, all with custom icons, it is impossible to see without checking which have subdocuments and which do not