Describe the bug

The algorithm 'PolarizationEfficiencyCor' accepts inputs in two formats, as a list of workspaces: InputWorkspaces property or as a group InputWorkspaceGroup.
If the name of a group workspace is put on the list of InputWorkspaces, mantid crashes.

To Reproduce

This script crashes mantid on the current nightly:

from mantid.simpleapi import *

names = []
for i in range(4):
    names.append(f'group_{i}')
    CreateWorkspace(DataX=np.linspace(0,5,6), DataY=[1]*5, OutputWorkspace=names[-1],Distribution=False, UnitX='Wavelength')
group = GroupWorkspaces(names)
ws=names[-1]
efficiencies= JoinISISPolarizationEfficiencies(F1=ws,F2=ws,P1=ws,P2=ws)
PolarizationEfficiencyCor(InputWorkspaces='group', OutputWorkspace='corr', Efficiencies=efficiencies)

Expected behavior

Probably the best would be to check this at the validation level: if there is a group on the list of input workspaces send error and warn the user with a message hinting at using the other property for groups.

Additional context