current data가 invalid한 경우 undefined로 설정
current data가 invalid한 경우 undefined로 설정

#869
current data가 invalid한 경우 undefined로 설정하여 getKmaStnHourlyWeather()에서 overwrite할 수 있게 한다.

kimalec/TodayWeather,WizardFactory/TodayWeather,seankim2/TodayWeather,seankim2/TodayWeather,kimalec/TodayWeather,WizardFactory/TodayWeather,kimalec/TodayWeather,skywlrl/TodayWeather,seankim2/TodayWeather,pokers/TodayWeather,kimalec/TodayWeather,seankim2/TodayWeather,pokers/TodayWeather,skywlrl/TodayWeather,WizardFactory/TodayWeather,skywlrl/TodayWeather,kimalec/TodayWeather,skywlrl/TodayWeather,skywlrl/TodayWeather,seankim2/TodayWeather,pokers/TodayWeather,pokers/TodayWeather,WizardFactory/TodayWeather,WizardFactory/TodayWeather,pokers/TodayWeather,seankim2/TodayWeather