toggle dSpacing plot creates min() arg error preventing refinement.

[mguthriem]

This issue arises when working with TOF neutron data and electing to toggle the display units from the default TOF to d-spacing in the Powder Pattern display tab. When this is done and a refinement cylce is requested, a pop-up with Refinement error: min() arg is an empty sequence appears. Toggling back to TOF removes this error and refinement can be initiated.

Attached is a gpx* file that exhibits the bug.

To test:

1. open gpx file
2. data are displayed in default TOF units
3. run a cyle of refinement: this is successful
4. toggle d-spacing view on data display
5. x-units convert to d-spacing
6. run a cycle of refinement: the error is observed.

!!!

SNAP058884.csv

*.gpx extensions are not allowed, so I changed this to .csv. It's not a .csv it's a .gpx !!!