Fix memleak

Closes #2307
(cherry picked from commit 6b176dfc)

modules/control/rc.c

@@ -1775,6 +1775,7 @@ static int VideoConfig( vlc_object_t *p_this, char const *psz_cmd,
                          VLC_VAR_GETLIST, &val, &text ) < 0 )
         {
             vlc_object_release( p_vout );
+            free( psz_value );
             return VLC_EGENERIC;
         }