Fix null device id

java -classpath "/android-sdk-macosx/tools/lib/ddmlib.jar:/android-sdk-macosx/tools/lib/x86_64/swt.jar:/appium/drpy/app/android/ScreenShooter.jar" io.appium.android.screenshooter.ScreenShooter null "/var/folders/wy/1786rjcd25x358xsx14h2cjr0000gn/T/appium11361-15943-imqm46.png"