cubicweb-vcwiki #3763204 Crash when previewing a new content [validation pending]

Preview button push just does not return in this case.

prioritynormal
typebug
done in0.2.0
load0.100
load left0.000
closed by#29ddb5c7ba84 [preview] Avoid a crash when previewing a page which has no content yet.
patch[preview] Avoid a crash when previewing a page which has no content yet. [applied]