Add NULL pointer checks to led sysfs file open & close helpers
Add NULL pointer checks to led sysfs file open & close helpers

Also emit a warning if file exists but can't be opened.

nemomobile/mce-plugin-libhybris,spiiroin/mce-plugin-libhybris,spiiroin/mce-plugin-libhybris,spiiroin/mce-plugin-libhybris,nemomobile/mce-plugin-libhybris,spiiroin/mce-plugin-libhybris,nemomobile/mce-plugin-libhybris,nemomobile/mce-plugin-libhybris