fix: -A not working (#503)

the imlib2 based multi-frame loader has not respected -A setting
since it's introduction in commit 76c2b81b.

also change multi.framedelay to `int` to avoid signedness change
warning.

Reviewed-on: https://codeberg.org/nsxiv/nsxiv/pulls/503
Reviewed-by: eylles <eylles@noreply.codeberg.org>

image.c

@@ -234,7 +234,8 @@ static bool img_load_multiframe(img_t *img, const fileinfo_t *file)
 		imlib_context_set_blend(!!(finfo.frame_flags & IMLIB_FRAME_BLEND));
 		imlib_blend_image_onto_image(frame, has_alpha, 0, 0, sw, sh, sx, sy, sw, sh);
 		m->frames[m->cnt].im = canvas;
-		m->frames[m->cnt].delay = finfo.frame_delay ? finfo.frame_delay : DEF_ANIM_DELAY;
+		m->frames[m->cnt].delay = m->framedelay ? m->framedelay :
+		                          (finfo.frame_delay ? finfo.frame_delay : DEF_ANIM_DELAY);
 		m->length += m->frames[m->cnt].delay;
 		m->cnt++;
 		img_free(frame, false);

nsxiv.h

@@ -180,7 +180,7 @@ typedef struct {
 	unsigned int cnt;
 	unsigned int sel;
 	bool animate;
-	unsigned int framedelay;
+	int framedelay;
 	int length;
 } multi_img_t;