lokdocview: check payload for inconsistencies before using it
lokdocview: check payload for inconsistencies before using it

Lets follow the old advice: "Be liberal in what you accept, be strict in
what you produce".

This is after noticing negative values for x, y in
the payload in some situation, such as, hitting a backspace key when the
cursor is at the start of a line

Change-Id: I11939b981f75969b88214baee66b4c69c5e41906

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