Script error on mobile app, doesn't occur on browser

Hi,

I encountered an error on mobile version of CRM:

TypeError: Cannot read property 'text' of null

It is caused by following line of code:

var statusofsell = Xrm.Page.getControl("header_process_statusofsell").getAttribute().getText();

"statusofsell" is a field on business process flow.

It doesn't occur on browser. (version 9)

I will be grateful for any suggestions!