eigenValuesNonSym: Set size of the output vector before filling it

Rather than assuming the caller has set it to the correct size already.
Setting the size in the method eigenValuesNonSym itself makes code
more robust.  Plus, the time needed for that should be negligible
compared to the actual eigenvalue computations.

dune/common/dynmatrixev.hh

@@ -73,6 +73,8 @@ namespace Dune {
           std::cerr << "For matrix " << matrix << " eigenvalue calculation failed! " << std::endl;
           DUNE_THROW(InvalidStateException,"eigenValues: Eigenvalue calculation failed!");
         }
+
+        eigenValues.resize(N);
         for (int i=0; i<N; ++i)
           eigenValues[i] = std::complex<double>(eigenR[i], eigenI[i]);
       }