NaNs in model state are not detected by physics data differences check

[jimmielin]

What happened?

Any NaN values in the model state go unreported by physics check against snapshot because the check is currently written as

if (diff > min_difference) then
   diff_count = diff_count + 1
end if

is always .false. and thus does not increment the count if diff is a NaN (NaN comparisons will always be false)

What are the steps to reproduce the bug?

Put in a NaN in any checked physics field

What CAM-SIMA hash were you using?

04a0b5a

What machine were you running CAM-SIMA on?

CISL machine (e.g. cheyenne)

What compiler were you using?

GNU

Path to a case directory, if applicable

No response

Will you be addressing this bug yourself?

Yes

Extra info

Will address with tracer_data PR