fix debug build on s390
fix debug build on s390

... by removing obsolete OSL_ENSURE. nVtableCall was renamed to
nFunctionIndex and the same check is done a couple of lines above.

Change-Id: Id52b69adceb337049c50a599aefc718498d688c0

JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core