[FIX] qunit-junit reporter: Add null-check for qunit DOM node
[FIX] qunit-junit reporter: Add null-check for qunit DOM node

This got broken with cf4228633b559d0b4f39721e2bf78d00b7c0e620

Change-Id: I5c86f9ea23c104ebb941cd59e06da9f66b8e703b
Fixes: https://github.com/SAP/karma-openui5/issues/14

cschuff/openui5,SAP/openui5,cschuff/openui5,SAP/openui5,SAP/openui5,SAP/openui5,cschuff/openui5