Silenced warning of clang: Changed NULL to nullptr as this should be used in C++11.

src/parser/DeterministicSparseTransitionParser.cpp

@@ -164,7 +164,7 @@ DeterministicSparseTransitionParser::DeterministicSparseTransitionParser(std::st
 	 */
 	LOG4CPLUS_INFO(logger, "Attempting to create matrix of size " << (maxnode+1) << " x " << (maxnode+1) << ".");
 	this->matrix = std::shared_ptr<storm::storage::SparseMatrix<double>>(new storm::storage::SparseMatrix<double>(maxnode + 1));
-	if (this->matrix == NULL) {
+	if (this->matrix == nullptr) {
 		LOG4CPLUS_ERROR(logger, "Could not create matrix of size " << (maxnode+1) << " x " << (maxnode+1) << ".");
 		throw std::bad_alloc();
 	}