We need to update the state of the button every time
when the frame's layout changes or when the selection
changes.
Show the button if the text frame is selected and it's
a floating table which would hang out of the actual page
after unfloating.

Change-Id: I6b64affb063f552921915a0735e80889e5fd8124
Reviewed-on: https://gerrit.libreoffice.org/65819
Tested-by: Jenkins
Reviewed-by: Tamás Zolnai <tamas.zolnai@collabora.com>