fix for issue Kiarash-Z#356

Author: juji

src/Calendar.js

@@ -44,6 +44,7 @@ const Calendar = ({
     };
     calendarElement.current.addEventListener('keyup', handleKeyUp, false);
     return () => {
+      calendarElement.current && 
       calendarElement.current.removeEventListener('keyup', handleKeyUp, false);
     };
   });