Clipboard is cleared after any DND move

Affected version

• Nightly flatpak: Yes
• Likely all versions since 2.24

Steps to reproduce

1. Copy file "A" to the clipboard (using CtrlC, for instance).
2. Move file "B" to another folder by drag-and-drop.
3. Paste (using CtrlV, for instance).

Current behavior

Nothing happens. Yet, the Paste action in the menu shows as sensible.

Expected behavior

A copy of file "A" is created at the destination (i.e., pasting works).

Additional information

This happens since commit 3befbe34, which fixed https://bugzilla.gnome.org/show_bug.cgi?id=532850.

It should only clear the clipboard if a file being moved was in the clipboard. But due to a mistake in the patch, it does so in all cases.