Return if the installing page isn't found

src/freedombone-installer

@@ -183,6 +183,10 @@ function before_setup_runs {
 
     curr_language=$(web_admin_get_language_subdir)
 
+    if [ ! -f "/usr/share/${PROJECT_NAME}/webadmin/${curr_language}/setup_installing.html" ]; then
+        return
+    fi
+
     cp "/usr/share/${PROJECT_NAME}/webadmin/${curr_language}/setup_installing.html" "$webadmin_install_dir/index.html"
 
     # get the username and domain from the setup.txt file