Guard entries!=NULL in comparison loop; fix load-all index to count-1

Agent-Logs-Url: https://github.com/kovidgoyal/kitty/sessions/8b314b99-cb92-4015-ab8e-89bb84994a97

Co-authored-by: kovidgoyal <1308621+kovidgoyal@users.noreply.github.com>

Author: Copilot

kitty/options/to-c.h

@@ -180,7 +180,7 @@ static inline void
 background_images(PyObject *src, Options *opts) {
     static unsigned generation = 0;
     size_t new_count = (PyTuple_Check(src) && PyTuple_GET_SIZE(src) > 0) ? (size_t)PyTuple_GET_SIZE(src) : 0;
-    if (new_count == opts->background_images.count) {
+    if (new_count == opts->background_images.count && opts->background_images.entries) {
         bool changed = false;
         for (size_t i = 0; i < new_count; i++) {
             const char *p = PyUnicode_AsUTF8(PyTuple_GET_ITEM(src, i));

kitty/state.c

@@ -275,7 +275,7 @@ increment_bg_image_idx(size_t idx, int delta) {
     }
     if ((unsigned)abs(delta) <= idx) return idx + delta;
     // wrap to last image, which means we need to load all
-    global_background_image(OPT(background_images).count);
+    if (OPT(background_images).count > 0) global_background_image(OPT(background_images).count - 1);
     return global_state.background_images.count ? global_state.background_images.count - 1 : 0;
 }