UBSan warning: variable length array with size 0 in rstto_image_list_set_compare_func

UBSan warns about undefined behavior when starting Ristretto:

../src/image_list.c:1075:22: runtime error: variable length array bound evaluates to non-positive value 0
    #0 0x56221bb3bb38 in rstto_image_list_set_compare_func ristretto/src/image_list.c:1075:5
    #1 0x56221bb3b2cf in rstto_image_list_set_sort_by_name ristretto/src/image_list.c:1101:5
    #2 0x56221bb6b554 in rstto_main_window_new ristretto/src/main_window.c:1470:13
    #3 0x56221bb6abec in main ristretto/src/main.c:117:18

Version info

0c12bb31 compiled on Arch Linux