Fix that malformed parameter values break the app

  When reading parameters from URL, an exception in case of a malformed
  URI sequence, make the app fail.

  This happens for instance when initializing the GWT logger
  system which breaks when checking the existence of the 'logLevel'
  parameter in the URL.

  We can see this behaviour just adding the 'x=%E4' parameter to
  any GWT app which reads url parameters in the beginning.

Bug: issue 7741
Change-Id: I3f941e835f70c4caf9dd9caa0f14b63003001584