blob limit for every single picture

bootsplash_file.h, line 100:

uint8_t num_blobs;

num_blobs for single image header can't be more than 255, so theme can contain unused blobs because there's no blob count check for every single picture:

bootsplash-packer.c, line 368:

	/* Set blob counts */
	for (blob_cur = blob_first; blob_cur; blob_cur = blob_cur->next) {
		if (blob_cur->header.picture_id < fh.num_pics)
			ph[blob_cur->header.picture_id].num_blobs++;
	}

I can set 450 for first image and 75 for second and the file will look like this:

—- File header —-

version: 55561

bg_red: 0
bg_green: 0
bg_blue: 0
bg_reserved: 0

num_blobs: 525
num_pics: 2

frame_ms: 40

—- Picture header —-

width: 200
height: 200

num_blobs: 194

position: 03x
position_offset: 0

anim_type: 1
anim_loop: 0

—- Picture header —-

width: 48
height: 48

num_blobs: 75

position: 53x
position_offset: 250

anim_type: 1
anim_loop: 0

525 != 194 + 75

This causes https://gitlab.manjaro.org/manjaro-arm/packages/extra/bootsplash-viewer/ to break