1. Open New Mission > Default Spacecraft > Ballistic/Mass panel
2. Type/Browse the SPAD SRP/SPAD Drag file. Click Apply.
3. Delete the fields with valid paths and click Apply to empty the File paths as in Default.
The error pops up 'The value "" for field "SPADSRPFile" is not an allowed value. The allowed values are: [ File must exist ]'
The code assumes that once the user has set a file name, it doesn't want to set a blank name after that.