app/internal/xkb: fix events sent when modifier keys are pressed

When modifier keys are active DispatchKey should not send a
key.EditEvent for the key that was pressed. For example when pressing
Ctrl+Alt+e DispatchEvent should not generate a key.EditEvent{Text:"e"}.

Signed-off-by: aarzilli <alessandro.arzilli@gmail.com>

app/internal/xkb/xkb_unix.go

@@ -185,7 +185,10 @@ func (x *Context) DispatchKey(keyCode uint32) (events []event.Event) {
 		C.xkb_compose_state_reset(x.compState)
 		str = x.utf8Buf[:size]
 	case C.XKB_COMPOSE_NOTHING:
-		str = x.charsForKeycode(kc)
+		mod := x.Modifiers()
+		if mod&(key.ModCtrl|key.ModAlt|key.ModSuper) == 0 {
+			str = x.charsForKeycode(kc)
+		}
 	}
 	// Report only printable runes.
 	var n int