Adding test for assert_equal_index with empty iterables (#29211)
Adding test for assert_equal_index with empty iterables (#29211)

* Adding test for assert_equal_index with empty iterables

* Adding issue # in comment

* formatted file using black

* Move test to indexes/multi/test_constructor.py

gfyoung/pandas,TomAugspurger/pandas,pandas-dev/pandas,dsm054/pandas,jorisvandenbossche/pandas,pandas-dev/pandas,datapythonista/pandas,rs2/pandas,gfyoung/pandas,TomAugspurger/pandas,datapythonista/pandas,datapythonista/pandas,jreback/pandas,pandas-dev/pandas,jorisvandenbossche/pandas,gfyoung/pandas,rs2/pandas,pandas-dev/pandas,TomAugspurger/pandas,gfyoung/pandas,rs2/pandas,jreback/pandas,jorisvandenbossche/pandas,gfyoung/pandas,dsm054/pandas,dsm054/pandas,jreback/pandas,jorisvandenbossche/pandas,datapythonista/pandas,jreback/pandas,dsm054/pandas,dsm054/pandas,jreback/pandas,rs2/pandas,TomAugspurger/pandas