fixed compilation with Sun compiler:
fixed compilation with Sun compiler:

".../pathfinder/compiler/algebra/algebra.c", line 815: warning: statement not reached
cc: acomp failed for .../pathfinder/compiler/algebra/algebra.c
gmake[6]: *** [liblogical_la-algebra.lo] Error 1

Removed `return NULL;` that could never be reached.

zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb