fix #653, spurious error in zygosityOfMutations()

Author: bhaller

core/individual.cpp

@@ -6384,17 +6384,20 @@ EidosValue_SP Individual_Class::ExecuteMethod_zygosityOfMutations(EidosGlobalStr
 	else
 	{
 		// When assessing a vector of mutations, we first determine which chromosomes we need to scan
-		// In this case we also need to check that all mutations belong to the same species as the individuals
-		if (Community::SpeciesForMutations(mutations_value) != species)
-			EIDOS_TERMINATION << "ERROR (Individual_Class::ExecuteMethod_zygosityOfMutations): zygosityOfMutations() requires that all mutations belong to the same species as the target individuals." << EidosTerminate();
+		Mutation **mutations_data = (Mutation **)mutations_value->ObjectData();
+		int mutations_count = mutations_value->Count();
+		
+		if (mutations_count > 0)
+		{
+			// In this case we also need to check that all mutations belong to the same species as the individuals
+			if (Community::SpeciesForMutations(mutations_value) != species)
+				EIDOS_TERMINATION << "ERROR (Individual_Class::ExecuteMethod_zygosityOfMutations): zygosityOfMutations() requires that all mutations belong to the same species as the target individuals." << EidosTerminate();
+		}
 
 		// zero out the scratch_ for all chromosomes; 0 indicates the chromosome is not active
 		for (Chromosome *chromosome : chromosomes)
 			chromosome->scratch_ = 0;
 
-		Mutation **mutations_data = (Mutation **)mutations_value->ObjectData();
-		int mutations_count = mutations_value->Count();
-		
 		focalMutations.resize(mutations_count);
 
 		Mutation **focalMutations_data = focalMutations.data();

eidos/eidos_interpreter.cpp

@@ -6437,7 +6437,7 @@ EidosValue_SP EidosInterpreter::Evaluate_For(const EidosASTNode *p_node)
 							case EidosValueType::kValueString:
 							{
 								EidosValue_String *string_range_value = (EidosValue_String *)(loop_handler.range_value.get());
-								std::string &iterator_logical_value = string_range_value->StringData_Mutable()[range_index];
+								const std::string &iterator_logical_value = string_range_value->StringData()[range_index];
 
 								*(std::string *)loop_handler.iterator_data = iterator_logical_value;
 								break;