fix warning

FWI/src/FWINonlinearSolvers.cpp

@@ -219,7 +219,7 @@ public:
           }
           FWD.CalculateDefect(dataObs, nonlinearEvaluation, defect, subproblems[prob]);
           if (FWD.GetReconstructionType() == "AllAtOnce" && substep == 0) {
-            defect[0].getVectorsWrite() = 0.0;
+            defect[0].getVectorsWrite().Clear();
           }
           mout << "after Defect " << PPM->TotalMemoryUsage() << endl;
           if (defect.size() != nonlinearEvaluation.size()) {