[MaL] abort if no ODE solver can be created.

And also in the tests prevent abort if no ODE solver can be created.

MathLib/ODE/ODESolverBuilder.h

@@ -10,6 +10,8 @@
 #ifndef MATHLIB_ODE_ODESOLVERBUILDER_H
 #define MATHLIB_ODE_ODESOLVERBUILDER_H
 
+#include <logog/include/logog.hpp>
+
 #include "ODESolver.h"
 #include "ConcreteODESolver.h"
 
@@ -38,9 +40,13 @@ std::unique_ptr<ODESolver<NumEquations>> createODESolver(
 #ifdef CVODE_FOUND
 	return std::unique_ptr<ODESolver<NumEquations>>(
 	    new ConcreteODESolver<CVodeSolver, NumEquations>(config));
-#else
-	return nullptr;
-#endif  // CVODE_FOUND
+#endif
+	(void)config;  // Unused parameter warning if no library is available.
+
+	ERR(
+	    "No ODE solver could be created. Maybe it is because you did not build"
+	    " OGS6 with support for any external ODE solver library.");
+	std::abort();
 }
 
 //! @}

Tests/MathLib/TestODESolver.cpp

@@ -66,6 +66,10 @@ template <unsigned NumEquations>
 std::unique_ptr<MathLib::ODESolver<NumEquations>> make_ode_solver(
     boost::property_tree::ptree const& conf)
 {
+	// Make sure testrunner does not crash if we haven't built with support for
+	// any external ODE solver lib.
+	if (!any_ode_solver_libs_available()) return nullptr;
+
 	BaseLib::ConfigTree config(conf, "", BaseLib::ConfigTree::onerror,
 	                           BaseLib::ConfigTree::onwarning);
 	return MathLib::createODESolver<NumEquations>(config);