removed spurious exception likely introduced in a merge

src/storm-gspn/parser/PnmlParser.cpp

@@ -283,7 +283,7 @@ namespace storm {
                 STORM_PRINT_AND_LOG("unknown multiplicity (node=arc): " + id + "\n");
             }
 
-            STORM_LOG_THROW(false, storm::exceptions::UnexpectedException, "No arc type specified for arc '" + id + "'");
+        
             if (type.second == "normal") {
                 builder.addNormalArc(source.second, target.second, multiplicity.second);
             } else if (type.second == "inhibition") {