fix simple_malloc malloc(0) behavior not to return non-unique pointers

src/malloc/__simple_malloc.c

@@ -15,6 +15,7 @@ void *__simple_malloc(size_t n)
 	static int lock;
 	size_t align=1;
 
+	if (!n) return 0;
 	if (n > SIZE_MAX/2) goto toobig;
 
 	while (align<n && align<ALIGN)