zipDirectory - when ZipFileEncoder is initialized with a password and there are subdirectories in the input directory => Null check operator used on a null value

[hrmoh]

Consider the following code:

var encoder = ZipFileEncoder(password: 'password');
encoder.zipDirectory(inputDir);

If there exist some directories inside inputDir, zipDirectory fails with the following execption:
Null check operator used on a null value
.