Add condition to handle empty input

[shivammathur]

This PR wraps the foreach loop in cs2pr script in an if condition to handle cases when simplexml_load_string will return false.

This will happen when

• Input xml file is empty or it does not exist
• 2 or more arguments are passed to the script.

Ref: https://www.php.net/manual/en/function.simplexml-load-string.php

[staabm]

thx. did similar changes in #4 but did not finish it yet.

I will merge this PR in the meantime as I dont have time to finish #4 in the next days

[staabm]

tagged a new release https://github.com/staabm/annotate-pull-request-from-checkstyle/releases/tag/1.0.1

[shivammathur]

Thanks for the quick release.

[staabm]

btw. do you agree that the case of emtpy input should exit with a non-zero exit-code, like I did it in https://github.com/staabm/annotate-pull-request-from-checkstyle/pull/4/files#diff-53aef30a2ab25806980a8b72fd6b9aecR43

?

[shivammathur]

In my opinion as the script creates annotations for errors, warnings in a tool's output, if the output is empty and no annotations are created the exit code should be zero.

[staabm]

I would expect a empty checkstyle result when no warnings/errors are contained, not a complete empty output

[shivammathur]

ok, in that case may be output a warning along with non-zero exit code.