Converts a time string in 12-hour format to 24-hour format. Returns an empty string if the input is invalid.
A string representing the time in 12-hour format (e.g., "2:15 PM")
The time formatted as 24-hour string ("HH:mm"), in local time zone.
Converts a time string in 12-hour format to 24-hour format. Returns an empty string if the input is invalid.