main/postmarketos-mkinitfs: fix mkbootimg call for devices w/o dtb (MR 1148)

Don't pass empty arguments to mkbootimg, when _second or _dt are not set.

main/postmarketos-mkinitfs/APKBUILD

 pkgname=postmarketos-mkinitfs
-pkgver=0.12.0
+pkgver=0.12.1
 pkgrel=0
 pkgdesc="Tool to generate initramfs images for postmarketOS"
 url="https://postmarketos.org"
@@ -41,5 +41,5 @@ sha512sums="5037cb7285bb7c0c40ca9e6df332d882ef9a8b379756c785f921e062dab1b7e7f313
 1d49db8a48ad513cc548b8a0ea23cc64518e71c93863155b4e9d2271fb46090506331c03d6955d693c8568c248ecc76b218efe4a6f6bba57c41c5f6d775dc61b  init.sh.in
 315cc6e8a73f9984e6843395d68734d26ac2fffce34039ec5f229ebcd818bdb353318398d6c824cede5d0b36e13d7589a1f1d3295d8162279b5dc6a2b939da88  init_functions.sh
 7201d4640a3e9ead8a47ffd9916b068476b7d950760a84c37e02268c942d49896bc986da6bdee27e832639c90775354d68046a6475205d8d1da995b068120d8f  mkinitfs.sh
-c448b6d8810deb85590ac9e4254a8390fd25b3c5f1aef0a49cfaa6d489c58d45f5f7bda376f87ce241a432aaeccf1046ba63bfda2508fd456f5a0a93e2ca6f7d  mkinitfs_functions.sh
+5105fcc5f2094009937b378c8d383270f4fcd0133d0e60268806a7d09966613f4ebfa93d7e1b90b5d83d0c5b1664a0b3fc7562e52cc1e0ca6cd54ff442b03e84  mkinitfs_functions.sh
 c7a3c33daeb12b33ac72207191941c4d634f15c22958273b52af381a70ebaba1d3a9299483f0c447d9e66c560151fe7b9588bb4bbef2c8914f83185984ee4622  mkinitfs_test.sh"

main/postmarketos-mkinitfs/mkinitfs_functions.sh

@@ -374,7 +374,7 @@ create_bootimg()
 			exit 1
 		fi
 	fi
-	# shellcheck disable=SC2039
+	# shellcheck disable=SC2039 disable=SC2086
 	mkbootimg-osm0sis \
 		--kernel "${kernelfile}" \
 		--ramdisk "$outfile" \
@@ -385,8 +385,8 @@ create_bootimg()
 		--ramdisk_offset "${deviceinfo_flash_offset_ramdisk}" \
 		--tags_offset "${deviceinfo_flash_offset_tags}" \
 		--pagesize "${deviceinfo_flash_pagesize}" \
-		"${_second}" \
-		"${_dt}" \
+		${_second} \
+		${_dt} \
 		-o "${outfile/initramfs-/boot.img-}" || exit 1
 	if [ "${deviceinfo_bootimg_blobpack}" = "true" ]; then
 		echo "==> initramfs: creating blob"