When reading an Associated Data List's sub-chunks JHOVE eats bytes
according to the value of the `bytesLeft` variable which is initialized
with the Associated Data List's size. Since the size encompasses not
only the sub-chunks but also the Associated Data List's 4 bytes sized
type ID field JHOVE should subtract 4 bytes from the `bytesLeft`
variable before it starts reading sub-chunks.

Those strings are NULL terminated, calling trim() removes the NULL byte.

It also removes all trailing whitespace, which may not be desired.
Something like `str.replaceFirst("\0$", "")` would be more precise.
Anyway, trim() is used in this commit to be consistent with the rest of
the WAVE module where trim() is used as well.