Prevent dividing by 0 when target-bitrate is 0.
Prevent dividing by 0 when target-bitrate is 0.

Change-Id: I05b7fb378b6b0c5f263e7839f96ba6830ee34fd2

webmproject/libvpx,GrokImageCompression/aom,mbebenita/aom,thdav/aom,liqianggao/libvpx,VTCSecureLLC/libvpx,ittiamvpx/libvpx-1,ShiftMediaProject/libvpx,ittiamvpx/libvpx-1,mwgoldsmith/vpx,openpeer/libvpx_new,shyamalschandra/libvpx,shacklettbp/aom,shyamalschandra/libvpx,luctrudeau/aom,goodleixiao/vpx,mbebenita/aom,ShiftMediaProject/libvpx,liqianggao/libvpx,running770/libvpx,goodleixiao/vpx,Topopiccione/libvpx,jmvalin/aom,zofuthan/libvpx,shyamalschandra/libvpx,stewnorriss/libvpx,felipebetancur/libvpx,smarter/aom,zofuthan/libvpx,mbebenita/aom,ittiamvpx/libvpx-1,openpeer/libvpx_new,smarter/aom,felipebetancur/libvpx,goodleixiao/vpx,smarter/aom,thdav/aom,mwgoldsmith/libvpx,felipebetancur/libvpx,felipebetancur/libvpx,ShiftMediaProject/libvpx,thdav/aom,mwgoldsmith/libvpx,liqianggao/libvpx,felipebetancur/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,shacklettbp/aom,Topopiccione/libvpx,jmvalin/aom,zofuthan/libvpx,webmproject/libvpx,stewnorriss/libvpx,running770/libvpx,shyamalschandra/libvpx,liqianggao/libvpx,GrokImageCompression/aom,mbebenita/aom,Topopiccione/libvpx,VTCSecureLLC/libvpx,luctrudeau/aom,jmvalin/aom,zofuthan/libvpx,mbebenita/aom,mbebenita/aom,Topopiccione/libvpx,shyamalschandra/libvpx,felipebetancur/libvpx,shyamalschandra/libvpx,running770/libvpx,mwgoldsmith/vpx,mwgoldsmith/libvpx,webmproject/libvpx,mbebenita/aom,smarter/aom,ittiamvpx/libvpx-1,ittiamvpx/libvpx-1,Topopiccione/libvpx,shacklettbp/aom,running770/libvpx,luctrudeau/aom,openpeer/libvpx_new,stewnorriss/libvpx,ShiftMediaProject/libvpx,luctrudeau/aom,running770/libvpx,goodleixiao/vpx,mwgoldsmith/libvpx,ittiamvpx/libvpx-1,VTCSecureLLC/libvpx,shacklettbp/aom,shacklettbp/aom,zofuthan/libvpx,openpeer/libvpx_new,mwgoldsmith/libvpx,VTCSecureLLC/libvpx,jmvalin/aom,stewnorriss/libvpx,smarter/aom,luctrudeau/aom,thdav/aom,stewnorriss/libvpx,webmproject/libvpx,thdav/aom,mwgoldsmith/vpx,stewnorriss/libvpx,jmvalin/aom,VTCSecureLLC/libvpx,goodleixiao/vpx,goodleixiao/vpx,mbebenita/aom,smarter/aom,running770/libvpx,luctrudeau/aom,mwgoldsmith/vpx,shacklettbp/aom,thdav/aom,liqianggao/libvpx,VTCSecureLLC/libvpx,openpeer/libvpx_new,mwgoldsmith/libvpx,Topopiccione/libvpx,mwgoldsmith/vpx,liqianggao/libvpx,GrokImageCompression/aom,GrokImageCompression/aom,zofuthan/libvpx,mwgoldsmith/vpx,webmproject/libvpx,jmvalin/aom,mbebenita/aom,openpeer/libvpx_new,GrokImageCompression/aom,GrokImageCompression/aom