scripts: add boot_patch unpack error catching

- failure to unpack wasn't being caught so boot_patch would continue to build a new cpio out of nothing and attempt to repack it (identified in #4049)

scripts/boot_patch.sh

@@ -86,6 +86,7 @@ ui_print "- Unpacking boot image"
 ./magiskboot unpack "$BOOTIMAGE"
 
 case $? in
+  0 ) ;;
   1 )
     abort "! Unsupported/Unknown image format"
     ;;
@@ -93,6 +94,9 @@ case $? in
     ui_print "- ChromeOS boot image detected"
     CHROMEOS=true
     ;;
+  * )
+    abort "! Unable to unpack boot image"
+    ;;
 esac
 
 [ -f recovery_dtbo ] && RECOVERYMODE=true
@@ -191,7 +195,7 @@ fi
 #################
 
 ui_print "- Repacking boot image"
-./magiskboot repack "$BOOTIMAGE" || abort "! Unable to repack boot image!"
+./magiskboot repack "$BOOTIMAGE" || abort "! Unable to repack boot image"
 
 # Sign chromeos boot
 $CHROMEOS && sign_chromeos