[Development] QtCore missing check for memory allocation

[Rainer Keller]

> because memory allocation can fail for a number of reasons, not only because you have requested a too large single chunk of memory.
Exactly, for example if other applications are consuming most of the memory.

> Furthermore people keep saying "What can we do if we detect a
> failed memory allocation? Qt is in an invalid state then and we have to
> crash anyway."
At least show a useful error message in any case. Right now the message
is SEGV.