Fixed gz decompress check for false

Previously if the decompressed value was, say, 0 an exception would be
thrown even though the decompression was successful. By making the check
for false strict the exception will still be thrown if there is an error
    in the underlying PHP functions, while allowing us to return
    decompressed values that would otherwise evaluate to false.
Merge branch 'hotfix/5752'

Close #5752
Fixes #5535
Merge pull request #5754 from adam-ja/hotfix/gz-decompress

Fixed gz decompress check for false
Merge branch 'hotfix/5754' into develop

Forward port #5754