BUG: Fixed bug in groupby(axis=1) with filter() throws IndexError, #11041
Fixed #11041 

On green now. Can you merge?
 merged via https://github.com/pydata/pandas/commit/ba5106ec753d820c1d61b330645b40bd43c97e62

thanks

note that we always to compare the results with an expected, and not just the index as this is a more general comparison.
