Fix T99955: Crash with 'Cache Result' and all render layers are disabled

Ensure render passes are allocated in the result prior to writing them.

Alternative could be to not write empty passes, but that is kind of
different from perspective of s one who reads the file.

Differential Revision: https://developer.blender.org/D15692

source/blender/render/intern/render_result.c

@@ -990,6 +990,8 @@ void render_result_exr_file_cache_write(Render *re)
   char str[FILE_MAXFILE + FILE_MAXFILE + MAX_ID_NAME + 100];
   char *root = U.render_cachedir;
 
+  render_result_passes_allocated_ensure(rr);
+
   render_result_exr_file_cache_path(re->scene, root, str);
   printf("Caching exr file, %dx%d, %s\n", rr->rectx, rr->recty, str);