np.linalg.qr: handle empty matrices #11412
Description
This may seem silly, but raising exceptions for mathematically legitimate request causes problems downstream.
See: dask/dask#3659 (weird case of distributed computation where there is an empty 0×n matrix that needs to be handled by np.linalg.qr; this happens when a distributed array of blocks blocks, called chunks in dask, are filtered, and it is unknown a priori which blocks, if any, are empty)
There are two cases, both of which are "mathematically legitimate":
- 0×n ->
qis 0×0 andris 0×n - m×0 ->
qis m×0 andris 0×0
If this suggestion is found to be reasonable, I'll create a PR.