Do not break if gemini report could not be opened
Do not break if gemini report could not be opened

Currently the test function throws an uncatched exception if the `open gemini-report/index.html` process could not be spawned after a test run.
An empty error handler has been added to catch that problem silently and do not break the whole process.
jmhomedes/sc5-styleguide-visualtest,SC5/sc5-styleguide-visualtest