Fix miscellaneous issues handling U. F. O. metadata.

This addresses the ampersand error and the corrupted real number problem from #1539 and a crash that occurred when I was working on those.

I'm just extending the original funny logic. If we were doing this right, we'd accept only numbers and dots here and would error on something that isn't compliant. If you don't see any reason not to do so, I might do that.