pvl_singleaxis produces an incorrect AOI when the sun is above the earth horizon but behind the module plane. Issue seems to be in [this line](https://github.com/sandialabs/MATLAB_PV_LIB/blob/c6211dec56c87b0e55ce7a6d5bbc64b206572f57/pvl_singleaxis.m#L203) of code. Similar to [issue 1221](https://github.com/pvlib/pvlib-python/issues/1221) for the python pvlib
pvl_singleaxis produces an incorrect AOI when the sun is above the earth horizon but behind the module plane.
Issue seems to be in this line of code.
Similar to issue 1221 for the python pvlib