fix use of uninitialized variable on error

Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>
(cherry picked from commit 2ee43275e3dfe528f9bc41f8520ba218487d0588)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

src/input/input.c

@@ -2356,7 +2356,7 @@ static int InputSourceInit( input_thread_t *p_input,
                             input_source_t *in, const char *psz_mrl,
                             const char *psz_forced_demux, bool b_in_can_fail )
 {
-    const char *psz_access, *psz_demux, *psz_path, *psz_anchor;
+    const char *psz_access, *psz_demux, *psz_path, *psz_anchor = NULL;
     char *psz_var_demux = NULL;
     double f_fps;