If the total duration of the differences of the log values
is 0.0 then just use the first log value.

open save dialog either in the user save directory or the last used
for saving files from the instruemnt view. Re #6130.

Not sure this is the best thing to do, ideally meanTime()
should be able to cope itself.

refs #6760

last commit introduced a bug instead of correcting. Now, only
exceptions related to no detector associated is ignored.

re #6061

(They were somehow 'lost' from a previous commit)

re #6061

If you don't load everything the resulting crop gives the wrong spectra
since it goes by index not spectrum and assumes an off-by-one value.

refs #6760

Refs #6757

re #6759