vesamenu: avoid strcmp() with NULL

Avoid touching memory at address zero when going from a background to
a non-background.

diff --git a/com32/menu/background.c b/com32/menu/background.c
index 49839cd..fa03441 100644 (file)
--- a/com32/menu/background.c
+++ b/com32/menu/background.c
@@ -18,7 +18,7 @@ const char *current_background = NULL;
 
 void set_background(const char *new_background)
 {
-  if (!current_background ||
+  if (!current_background || !new_background ||
       strcmp(current_background, new_background)) {
     draw_background(new_background);
     current_background = new_background;