Fix NULL pointer dereferences after malloc

This adds missing NULL checks after memory allocation in multiple core
files to prevent crashes when malloc fails.

Author: jserv

src/image-gif.c

@@ -554,7 +554,18 @@ static twin_animation_t *_twin_animation_from_gif_file(const char *path)
 
     anim->n_frames = frame_count;
     anim->frames = malloc(sizeof(twin_pixmap_t *) * frame_count);
+    if (!anim->frames) {
+        free(anim);
+        gif_close(gif);
+        return NULL;
+    }
     anim->frame_delays = malloc(sizeof(twin_time_t) * frame_count);
+    if (!anim->frame_delays) {
+        free(anim->frames);
+        free(anim);
+        gif_close(gif);
+        return NULL;
+    }
 
     gif_rewind(gif);
     uint8_t *color, *frame;

src/path.c

@@ -581,6 +581,8 @@ twin_path_t *twin_path_create(void)
     twin_path_t *path;
 
     path = malloc(sizeof(twin_path_t));
+    if (!path)
+        return NULL;
     path->npoints = path->size_points = 0;
     path->nsublen = path->size_sublen = 0;
     path->points = 0;

src/poly.c

@@ -302,6 +302,8 @@ void twin_fill_path(twin_pixmap_t *pixmap,
 
     int nalloc = path->npoints + path->nsublen + 1;
     twin_edge_t *edges = malloc(sizeof(twin_edge_t) * nalloc);
+    if (!edges)
+        return;
     int p = 0;
     int nedges = 0;
     for (int s = 0; s <= path->nsublen; s++) {

src/window.c

@@ -208,6 +208,8 @@ void twin_window_set_name(twin_window_t *window, const char *name)
     window->name = malloc(strlen(name) + 1);
     if (window->name)
         strcpy(window->name, name);
+    else
+        window->name = NULL; /* Ensure consistent state on allocation failure */
     twin_window_draw(window);
 }