Fix crash on loading saves with produce()d objects (#765)

Thanks @melex750!

src/script/scriptfunc.cpp

@@ -1393,6 +1393,7 @@ bool CScriptFunctions::rProduce(CBotVar* var, CBotVar* result, int& exception, v
             CProgramStorageObject* programStorage = dynamic_cast<CProgramStorageObject*>(object);
             Program* program = programStorage->AddProgram();
             programStorage->ReadProgram(program, name2.c_str());
+            program->readOnly = true;
             program->filename = name;
             dynamic_cast<CProgrammableObject*>(object)->RunProgram(program);
         }