How to reproduce: In snippet generator choose 'checkout: general SCM', in SCM choose Git, put 'gitlab' in 'repository browser' and a number in a 'Version' field.
If string is put in 'Version' the error is printed: Can't convert ''8.0'' to a number: For input string: "'8.0'"
If number is put in 'Version', e.g. 8.0, the following error occurs during pipeline execution:
java.lang.ClassCastException: hudson.plugins.git.browser.GitLab.version expects class java.lang.String but received class java.math.BigDecimal