initialize _laxFriedrich in tracer2d

modules/shallowWater/dgConservationLawShallowWaterTracer2d.cpp

@@ -227,6 +227,7 @@ dgConservationLawShallowWaterTracer2d::dgConservationLawShallowWaterTracer2d() :
   _g = gdefault;
   _alphaMovingBathWD = 0.0;
   _useMovingBathWD = false;
+  _laxFriedrichs = false;
   _bathymetry = NULL;
   _hydro = NULL;
   _originalBathymetry = NULL;