fix: Check for install list before attempting to install flatpaks

Author: EyeCantCU

system_files/desktop/usr/bin/ublue-flatpak-system-install

@@ -1,5 +1,7 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
-cat /etc/flatpak/install | while read line; do
-  flatpak install --system --noninteractive --no-pull flathub $line
-done && mv /etc/flatpak/install /etc/flatpak/installed
+if [[ -f '/etc/flatpak/install' ]]; then
+  cat /etc/flatpak/install | while read line; do
+    flatpak install --system --noninteractive --no-pull flathub $line
+  done && mv /etc/flatpak/install /etc/flatpak/installed
+fi