Add a general imagespace in case of adding non img-elements
It is quite easily to add different elements than images to the CE "Text w image" but the problem is, that the <dl> around each element will get no width and so it is not possible to position the element correctly.
So if the width is 0 (which is the case at non-images), take the value of the imagewidth-field of the Backend.
As videos, flashes are getting very common inside websites it would be cool to allow it to happen inside Text w Image too.
(issue imported from #M6902)