Fix pasting from SailfishOS clipboard to fingerterm.

Commit 90734807 broke the internal copy/paste in Fingerterm under SailfishOS, and the external (to/from other Sailfish apps) copying has not worked ever.

This patch fixes the internal copy/paste, and makes copying form Sailfish clipboard to Fingerterm possible.

The other direction still does not work, i.e. fingerterm clipboard contents are not transmitted to other SailfishOS apps.