"""Convert a duration in seconds into a human-readable string format.

The function formats the given duration in seconds into a more readable string, 
representing the duration in days, hours, minutes, or seconds, depending on the 
magnitude of the input. The function handles edge cases such as durations less 
than 1 second and ensures the output is grammatically correct (e.g., '1 min' 
instead of '1 mins').

Args:
    secs (float): The duration in seconds to be formatted. Must be a non-negative 
                 number.

Returns:
    str: A human-readable string representing the duration. The string will be in 
         one of the following formats: 'X days', 'X hrs', 'X mins', 'X secs', or 
         '0 secs' if the duration is less than 1 second. If an error occurs during 
         processing, an empty string is returned.

Raises:
    This function does not explicitly raise exceptions but returns an empty string 
    if an error occurs during processing.
"""
You should write code starting with:
def format_timer(secs: float) -> str:
    pass

