backends: ignore missing monitor config files

src/backends/hyprland-backend.vala

@@ -183,9 +183,13 @@ namespace TunerDisplays {
 
         private static Gee.HashMap<string, SavedMonitor> read_saved_monitors() {
             var monitors = new Gee.HashMap<string, SavedMonitor>();
+            var path = monitors_path();
+            if (!FileUtils.test(path, FileTest.EXISTS))
+                return monitors;
+
             try {
                 string content;
-                if (!FileUtils.get_contents(monitors_path(), out content))
+                if (!FileUtils.get_contents(path, out content))
                     return monitors;
 
                 foreach (var line in content.split("\n")) {

src/backends/niri-backend.vala

@@ -138,9 +138,13 @@ namespace TunerDisplays {
 
         private static Gee.HashMap<string, SavedMonitor> read_saved_monitors() {
             var monitors = new Gee.HashMap<string, SavedMonitor>();
+            var path = monitors_path();
+            if (!FileUtils.test(path, FileTest.EXISTS))
+                return monitors;
+
             try {
                 string content;
-                if (!FileUtils.get_contents(monitors_path(), out content))
+                if (!FileUtils.get_contents(path, out content))
                     return monitors;
 
                 string current_name = "";