frame-drag-and-drop: backport fix in 5fdb5cf
frame-drag-and-drop: backport fix in 5fdb5cf

Fix made by @scymtym. Also we do the same in other function parts to
have consistent code.

Original commit message:

frames: fix rare drag-and-drop-related error

Without this changes, dragging a presentation over across multiple
panes would sometimes try to unhighlight the presentation on some pane
using an event from a different pane and thus potentially signal an
error or behave incorrectly.

slyrus/mcclim,slyrus/mcclim