src/gui/text: whitespace fixes

Change-Id: Idd0e0673d76a23593b03558e18bc6afbdb9b38ab
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Evdev keyboard handler emits keyevents with QString(0xffff)

Key events that have no text representation are by the evdevkeyboard
emitted as a QString(0xffff). Other keyboard event handlers appear to
all emit key events with null strings for these events.

Change-Id: If6b5c61a8cb76a6843238f834ce4feb4b73aa199
Reviewed-by: Gunnar Sletta <gunnar.sletta@digia.com>