better error message when trying to open file with editor

editor/src/editor/main.rs

@@ -330,6 +330,8 @@ fn run_event_loop(file_path_opt: Option<&Path>) -> Result<(), Box<dyn Error>> {
                         )
                     }
                 } else {
+                    begin_render_pass(&mut encoder, &frame.view, &ed_theme);
+
                     queue_no_file_text(
                         &size,
                         NOTHING_OPENED,

editor/src/editor/resources/strings.rs

@@ -1,3 +1,3 @@
-pub const NOTHING_OPENED: &str = "Execute `cargo run edit <filename>` to open a file.";
+pub const NOTHING_OPENED: &str = "Opening files is not yet supported. Execute `cargo run edit` from the root folder of the repo to try the editor.";
 pub const START_TIP: &str =
     "Start by typing '[', '{', '\"' or a number.\nInput chars that would create parse errors will be ignored.";