FLUID-5364: corrected use of ._setErr

There were attempts at accessing ._setErr off of the "that" object, but the function was never defined for it. The correct form was to use the global function fluid.XMLP._setErr
Merge branch 'master' into FLUID-5364
Merge remote-tracking branch 'jobara/FLUID-5364'

* jobara/FLUID-5364:
  FLUID-5364: corrected use of ._setErr