We should exit the idle calc when the sheet changes.
We should exit the idle calc when the sheet changes.

Otherwise the code would end up in an undefined state.

Change-Id: I47f58698ac1eb94bf92ab7278bb7521d892ba340

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