LoadMD + FileBackEnd: error messages when ticking combinations of options

[Federico M Pouzols]

This is really minor, I don't think it deserves a ticket or branch, just noting it down here. It could be fixed when any other changes/additions are done in LoadMD, FileBackEnd and friends.

I'm going to load the big file 22413_22932_SQW.nxs:

• If I select FileBackEnd and BoxStructureOnly but not MetadataOnly, an error (exception) will tell me: "Both BoxStructureOnly and fileBackEnd were set to TRUE: this is not possible." That looks fine.

• But if I select FileBackEnd and MetadataOnly, but not BoxStructureOnly, the same throw will tell me the same "Both BoxStructureOnly and fileBackEnd were set to TRUE: this is not possible.", even though I didn't selected BoxStructureOnly.

This seems to come down to how m_BoxStructureAndMethadata is used in the if that throws that exception.

[Stuart Campbell]

This ticket has been transferred to github issue ​12442