Calling Job.setParameterValue() with null value doesn't remove the parameter

[Nicklas Nordborg]

The Job.setParameterValue() and Job.setParameterValues() methods are two variants for setting a parameter to a job. The first set a single value, while the second set a list of values. Passing 'null' as the value should remove the parameter, but this only happens in the latter method. The first will keep that parameter with a null value.

[Nicklas Nordborg]

In 7877:

Fixes #2228: Calling Job.setParameterValue() with null value doesn't remove the parameter