input: fix forward NULL

(cherry picked from commit dd6170364ffa7a6cc2248f2ef8b1f98e25f95589)

src/input/control.c

@@ -530,9 +530,13 @@ static void UpdateBookmarksOption( input_thread_t *p_input )
     }
 
     char *psz_value = malloc( i_len + p_input->p->i_bookmark + 1 );
-    char *psz_next = psz_value;
 
-    psz_next += sprintf( psz_next, "bookmarks=" );
+    if( psz_value != NULL )
+    {
+        strcpy( psz_value, "bookmarks=" );
+
+        char *psz_next = psz_value + strlen( "bookmarks" );
+
         for( int i = 0; i < p_input->p->i_bookmark && psz_value != NULL; i++ )
         {
             const seekpoint_t *p_bookmark = p_input->p->pp_bookmark[i];
@@ -545,13 +549,15 @@ static void UpdateBookmarksOption( input_thread_t *p_input )
             if( i < p_input->p->i_bookmark - 1)
                 *psz_next++ = ',';
         }
+    }
     vlc_mutex_unlock( &p_input->p->p_item->lock );
 
-    if( psz_value )
-        input_item_AddOption( p_input->p->p_item, psz_value, VLC_INPUT_OPTION_UNIQUE );
-
+    if( psz_value != NULL )
+    {
+        input_item_AddOption( p_input->p->p_item, psz_value,
+                              VLC_INPUT_OPTION_UNIQUE );
         free( psz_value );
-
+    }
     input_SendEventBookmark( p_input );
 }