Imaging linear to stokes I gives cryptic error

[timcornwell]

When the output image is stokeI but the input visibility is e.g. linear, the resulting error message is very cryptic:

File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/rascil-0.1.2-py3.7.egg/rascil/processing_components/griddata/gridding.py", line 239, in grid_visibility_to_griddata
cf.data[chan, :, zzc, vvf, uuf, :, :] * v[:, numpy.newaxis, numpy.newaxis]
ValueError: non-broadcastable output operand with shape (1,6,6) doesn't match the broadcast shape (4,6,6)

The case should either be handled correctly or a better error message emitted.

[timcornwell]

Moved to https://gitlab.com/ska-telescope/rascil.git