Memory leak in mapfile.c:loadMapInternal in error cases

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In loadMapInternal, at around line 4521 of mapfile.c, memory is allocated for a mapObj and a pointer to it 
stored in `map'.  In no cases that an error occurs is `map' deallocated before returning NULL when an 
error is encountered while loading the map file.  This will result in the memory `map' points to leaking, as 
well as any memory that it "owns" as a result of the partial loading of the map file.