BUG: combining frame with empty frame still unions index. #2307
BUG: combining frame with empty frame still unions index. #2307

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