Description of problem:
For some process definitions the BPMN2 source in the source view does not show line numbers for closing XML elements. See lastLineNumberMissing image.

Steps to Reproduce:
1. Create a process Start -> Task -> Task -> End
2. Display the BPMN2 source view

Actual results:
Line numbers missing for XML closing elements (e.g. </bpmn2:definition>

Expected results:
All line numbers are present as in the lineNumbersOk image which is a process start -> task -> task -> task -> end