Cleaned up property fetching

comdel/domain/comdelgenerator.cpp

@@ -396,11 +396,12 @@ optional<Pin> ComdelGenerator::loadPin(PinNode node)
 }
 
 int getIntProperty(DisplayItemNode &node, std::string property) {
-    for(auto prop: node.values) {
+    for(auto& prop: node.values) {
         if(prop.key.value == property) {
             return prop.value.asInt();
         }
     }
+    throw std::exception();
 }
 
 std::optional<Display> ComdelGenerator::loadDisplay(DisplayNode node)