Extend processWhere call

[ctgh]

Description

Extend the call to processWhere to match the new signature introduced in JCSDA-internal/ufo#3258

This is a neutral change; if the empty string is used in the final argument then no caching is performed.

Issue(s) addressed

No issue - tiny change

Dependencies

Please merge at the same time as JCSDA-internal/ufo#3258

Impact

N/A

Checklist

• I have updated the unit tests to cover the change
• New functions are documented briefly via Doxygen comments in the code
• I have linted my code using cpplint
• I have run the unit tests
• I have run mo-bundle to check integration with the rest of JEDI and run the unit tests under all environments

[ctgh]

I forgot that I have closed the associated ufo PR for now. I intend to run some performance tests in order to quantify any benefits this may bring.