Fix COLOR_SCHEME when commands exit with error

Fix #57

Author: TheTumultuousUnicornOfDarkness

linuxdeploy-plugin-gtk.sh

@@ -226,9 +226,9 @@ mkdir -p "$HOOKSDIR"
 cat > "$HOOKFILE" <<\EOF
 #! /usr/bin/env bash
 
-COLOR_SCHEME="$(dbus-send --session --dest=org.freedesktop.portal.Desktop --type=method_call --print-reply --reply-timeout=1000 /org/freedesktop/portal/desktop org.freedesktop.portal.Settings.Read 'string:org.freedesktop.appearance' 'string:color-scheme' 2>/dev/null | tail -n1 | cut -b35- | cut -d' ' -f2)"
+COLOR_SCHEME="$(dbus-send --session --dest=org.freedesktop.portal.Desktop --type=method_call --print-reply --reply-timeout=1000 /org/freedesktop/portal/desktop org.freedesktop.portal.Settings.Read 'string:org.freedesktop.appearance' 'string:color-scheme' 2> /dev/null | tail -n1 | cut -b35- | cut -d' ' -f2 || printf '')"
 if [ -z "$COLOR_SCHEME" ]; then
-    COLOR_SCHEME="$(gsettings get org.gnome.desktop.interface color-scheme 2> /dev/null)"
+    COLOR_SCHEME="$(gsettings get org.gnome.desktop.interface color-scheme 2> /dev/null || printf '')"
 fi
 case "$COLOR_SCHEME" in
     "1"|"'prefer-dark'")  GTK_THEME_VARIANT="dark";;