Remove wrong assert from QMetaType.

Remove wrong assert from QMetaType.

We can't assert that QMetaType helper arrays are initialized. In rare
situations it may happen that QMetaType compiled without support for an
external type (without compiled Gui or Widgets libraries) will be asked
for additional information for the type.

For example (assuming Qt is compiled with --no-gui):
// typeId it may be received over network (QMetaType::QImage)
void *ptr = QMetaType::create(typeId);

Change-Id: I018a59b23def35c7574e7c921019b5db4f06e800
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>