TST: NaN in MultiIndex should not become a string (#7031) (#16625)
TST: NaN in MultiIndex should not become a string (#7031) (#16625)


rs2/pandas,pratapvardhan/pandas,pratapvardhan/pandas,nmartensen/pandas,GuessWhoSamFoo/pandas,toobaz/pandas,DGrady/pandas,amolkahat/pandas,louispotok/pandas,TomAugspurger/pandas,jreback/pandas,linebp/pandas,amolkahat/pandas,cbertinato/pandas,pratapvardhan/pandas,winklerand/pandas,cbertinato/pandas,jreback/pandas,dsm054/pandas,MJuddBooth/pandas,DGrady/pandas,rs2/pandas,amolkahat/pandas,MJuddBooth/pandas,toobaz/pandas,rs2/pandas,dsm054/pandas,harisbal/pandas,toobaz/pandas,DGrady/pandas,linebp/pandas,kdebrab/pandas,pandas-dev/pandas,zfrenchee/pandas,MJuddBooth/pandas,TomAugspurger/pandas,winklerand/pandas,jmmease/pandas,winklerand/pandas,cbertinato/pandas,pandas-dev/pandas,jorisvandenbossche/pandas,zfrenchee/pandas,datapythonista/pandas,DGrady/pandas,zfrenchee/pandas,harisbal/pandas,harisbal/pandas,GuessWhoSamFoo/pandas,jreback/pandas,Winand/pandas,datapythonista/pandas,winklerand/pandas,nmartensen/pandas,jmmease/pandas,Winand/pandas,nmartensen/pandas,GuessWhoSamFoo/pandas,toobaz/pandas,Winand/pandas,nmartensen/pandas,MJuddBooth/pandas,cbertinato/pandas,cython-testbed/pandas,zfrenchee/pandas,dsm054/pandas,gfyoung/pandas,louispotok/pandas,dsm054/pandas,louispotok/pandas,Winand/pandas,winklerand/pandas,linebp/pandas,pratapvardhan/pandas,pandas-dev/pandas,pandas-dev/pandas,jmmease/pandas,jorisvandenbossche/pandas,rs2/pandas,DGrady/pandas,kdebrab/pandas,jorisvandenbossche/pandas,jmmease/pandas,cbertinato/pandas,jmmease/pandas,louispotok/pandas,zfrenchee/pandas,cython-testbed/pandas,jreback/pandas,louispotok/pandas,datapythonista/pandas,cython-testbed/pandas,GuessWhoSamFoo/pandas,gfyoung/pandas,harisbal/pandas,linebp/pandas,gfyoung/pandas,dsm054/pandas,Winand/pandas,cython-testbed/pandas,jreback/pandas,kdebrab/pandas,winklerand/pandas,harisbal/pandas,gfyoung/pandas,gfyoung/pandas,datapythonista/pandas,DGrady/pandas,MJuddBooth/pandas,jmmease/pandas,linebp/pandas,kdebrab/pandas,jorisvandenbossche/pandas,linebp/pandas,amolkahat/pandas,GuessWhoSamFoo/pandas,cython-testbed/pandas,amolkahat/pandas,toobaz/pandas,nmartensen/pandas,kdebrab/pandas,TomAugspurger/pandas,pratapvardhan/pandas,TomAugspurger/pandas,Winand/pandas,nmartensen/pandas