Background data files with only one time bin don't work as expected in OSPEX

[samaloney]

E.g. this file solo_L1_stix-sci-xray-cpd_20210521T013011-20210521T031011_V01_2105210020-54527.fits essentially the mrdfits procedure seems to drop dimension of size one or at least compared to python. The count array should have dimensions 32, 12, 32, 1 but after reading it has dimension 32, 12, 32. I found that by hacking the shape data_str_bk.counts = reform(data_str_bk.counts, [32,12,32,1]) of the counts array before line 114 of stx_convert_science_data2ospex.pro it worked as expected.

This could be a more wide spread issue need to test how data with one detector, pixel, or energy work or is it only leading or trailing dimension of size 1 that are dropped.