"invalid q range: qmin must be smaller than qmax" on a number of models

[ajj]

From Paul Butler's testing on 28th August 2016:

"On the other hand spherical_sld, lamellar_stack_paracrystal, stacked_disk and square_well all generate a very strange error before giving appearing to work "invalid q range: qmin must be smaller than qmax" note that in these tests the condition is always true as it is just the default qmin and qmax in the fitpage."