multiphase adaption criterion: some improvements

now all phases are considered and a potential division by zero (if all
the saturations of a phase are zero) is avoided.

examples/problems/lensproblem.hh

@@ -372,7 +372,6 @@ public:
     void endTimeStep()
     {
 #ifndef NDEBUG
-        /*
         this->model().checkConservativeness();
 
         // Calculate storage terms
@@ -383,7 +382,6 @@ public:
         if (this->gridView().comm().rank() == 0) {
             std::cout << "Storage: " << storage << std::endl << std::flush;
         }
-        */
 #endif // NDEBUG
     }