Fix Emits of Additional ANSI Characters

This commit ensures that ANSI chars won't be emitted when pressing
non-standard modifier keys.

Fixes wez#4975

window/src/os/x11/keyboard.rs

@@ -396,7 +396,17 @@ impl KeyboardWithFallback {
                             }
                             _ => sym,
                         }
-                    } else if kc.is_none() && key_code_from_sym.is_none() {
+                    } else if kc.is_none()
+                        && key_code_from_sym.is_none()
+                        // Make sure that none-standard modifier keys of Neo2 layout are not mapped
+                        // te a fallback because that would result in extra emitions of the
+                        // original ANSI characters
+                        && !matches!(
+                            xsym,
+                            xkbcommon::xkb::Keysym::ISO_Level3_Shift
+                                | xkbcommon::xkb::Keysym::ISO_Level5_Shift
+                        )
+                    {
                         // Not sure if this is a good idea, see
                         // <https://github.com/wez/wezterm/issues/4910> for context.
                         match fallback_feed {