Fix previous commit: Do not call memset() if realloc() returned NULL.

apt-pkg/contrib/mmap.cc

@@ -461,10 +461,11 @@ bool DynamicMMap::Grow() {
 			return false;
 
 		Base = realloc(Base, newSize);
-		/* Set new memory to 0 */
-		memset((char*)Base + WorkSpace, 0, newSize - WorkSpace);
 		if (Base == NULL)
 			return false;
+		else
+			/* Set new memory to 0 */
+			memset((char*)Base + WorkSpace, 0, newSize - WorkSpace);
 	}
 
 	Pools =(Pool*) Base + poolOffset;