[A/U/FileConverter] OGS2VTK: Check result.

Applications/Utils/FileConverter/OGS2VTK.cpp

@@ -48,6 +48,10 @@ int main (int argc, char* argv[])
 
     std::unique_ptr<MeshLib::Mesh const> mesh(
         MeshLib::IO::readMeshFromFile(mesh_in.getValue()));
+    if (!mesh)
+    {
+        return EXIT_FAILURE;
+    }
     INFO("Mesh read: %d nodes, %d elements.", mesh->getNumberOfNodes(),
          mesh->getNumberOfElements());