The parser does not know whether the constant proplist it is about to fill
is missing because it was overwritten by a later local/constant, or because
the preparser was interrupted by a script error and didn't store its
proplist. Thus, the parser cannot simply give up at that point, and in
order to keep things simple it creates a throwaway proplist. This proplist
was thrown away too soon, though.
Thanks to Zapper for the testcase.
Sven Eberhardt