paste after splitting or unsplitting (fixes #2142186).
Note: this is a workaround for an issue with Scintilla where the
widget (or its parents) can't be removed or reparented to a
non-visible widget.


git-svn-id: https://geany.svn.sourceforge.net/svnroot/geany/trunk@3044 ea778897-0a13-0410-b9d1-a72fbfd435f5