D9732: Fix for xembedsniproxy crash due to NULL returned from xcb_image_get()

[Kai Uwe Broulik]

broulik added reviewers: Plasma, davidedmundson.

REPOSITORY
  R120 Plasma Workspace

REVISION DETAIL
  https://phabricator.kde.org/D9732

To: maciejsitarz, #plasma, davidedmundson
Cc: plasma-devel, ZrenBot, progwolff, lesliezhai, ali-mohamed, jensreuterberg, 
abetts, sebas, apol, mart