libsemanage: semanage_store: fix segfault introduced to fix memory leak

In the patch to fix a minor memory leak, I introduced a garuanteed
segfault.  The point to the stack variable will never be NULL, whereas
the value on the stack will be.

Signed-off-by: Eric Paris <eparis@redhat.com>

libsemanage/src/semanage_store.c

@@ -796,7 +796,7 @@ static int append_arg(char ***argv, int *num_args, const char *arg)
 {
 	char **a;
 
-	a = realloc(argv, sizeof(**argv) * (*num_args + 1));
+	a = realloc(*argv, sizeof(**argv) * (*num_args + 1));
 	if (a == NULL)
 		return -1;