跟系统键盘来回切换可能导致的问题

lib/keyboards/keyboard_manager.dart

@@ -219,7 +219,7 @@ class CoolKeyboard {
       //   }
       // });
       if (animation) {
-        _pageKey!.currentState!.exitKeyboard();
+        _pageKey!.currentState?.exitKeyboard();
         Future.delayed(Duration(milliseconds: 116)).then((_) {
           _root!.clearKeyboard();
         });