Rearrange array to single level

The goal is to flatten the array into a single list and remove any empty elements.

Input

[
    []  ,
    [''],
    ['0', '1', '2'],
    ['3', '4', '5'],
    ['6', '7'],
    ['8', '9'],
    ['']
]

Output

['', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '']