ThermalNuetronBk2BkExpConvPV throws unexpected exception when used among fit functions

[abuts]

If one tries to look at ThermalNuetronBk2BkExpConvPV using fit functions interface:

1)View->fit function

2)Load WB vanadium and look at monitor spectra (do not think it is essential but who knows) The WB spectra on monitor looks similar to the one, described in the wiki.

3)Functions->Add Function ->ThermalNuetronBk2BkExpConvPVogit

4. Set up ws fitting ranges and ws spectra

5. Setup-> find peak.

Throws scary exception:

Unexpected exception: ThermalNuetronBk2BkExpConvPV: do not allow to set peak's centre

is thrown.

The function should either accept setting peaks (preferably) or handle unexpected situation more gently

Unexpected exception: ThermalNuetronBk2BkExpConvPV: do not allow to set peak's centre

Apparently this function needs a method, which allows to set pulse centre

It may be wiki is confusing but working with this function from fitting interface generates the range of problems

1. needed -- safeguards for fitting interface.
2. sample of parameters, which would allow to see something on the plot.
3. some modifications of the wiki page, which allows to relate the parameters from the table to the parameters from the formula. In addition, there is "Sigma and Gamma " statements under the formula, but only Sigma can be identified from the formula.

[abuts]

This issue was originally trac ticket 6716