Undefined variable $extensions_to_check in nagios_check_requirements()

Please review. If the automated tests had worked, this would have been noticed during the test.

Marking Critical, since Nagios isn't working at all right now due to this.

This is a patch of the MR, for ease of use with composer patches.

@Gogowitsch, @greg.harvey, @hoanns, @kbahey, @McChicken, @instanceofjamie please release an new tagged version to restore funktioniality.

Thanks for your work, @solideogloria and @sleitner! I’ll release a new version later today. I am currently testing.

I have released 1.19 → and my production server is green again.

I am deeply sorry for the time you have lost due to my poor quality assurance of the previous release! I have marked it as broken.

No problem. Thanks.

Automatically closed - issue fixed for 2 weeks with no activity.