always queue_popup() in details view on right click (#421)

This makes rightclick+drag in details view bring up the GDK_ACTION_ASK menu for the dragged file. This behavior was prior to this commit not present when an item was dragged from the NAME column.

Related issues:
#421 (closed) right click drag behave the same on all columns in list view
#208 (closed) 1.8.x Regression: right-click drag and drop does not show a context menu on drop any more