fix android physical keyboard input

Signed-off-by: fufesou <shuanglongchen@yeah.net>

flutter/lib/models/input_model.dart

@@ -64,7 +64,7 @@ class InputModel {
   InputModel(this.parent);
 
   KeyEventResult handleRawKeyEvent(FocusNode data, RawKeyEvent e) {
-    if (!stateGlobal.grabKeyboard) {
+    if (isDesktop && !stateGlobal.grabKeyboard) {
       return KeyEventResult.handled;
     }