Debug: Enable inspecting non-GRF objects

src/table/newgrf_debug_data.h

@@ -1290,13 +1290,14 @@ static const NIVariable _niv_objects[] = {
 };
 
 class NIHObject : public NIHelper {
-	bool IsInspectable(uint index) const override        { return ObjectSpec::GetByTile(index)->grf_prop.grffile != nullptr; }
+	bool IsInspectable(uint index) const override        { return true; }
+	bool ShowExtraInfoOnly(uint index) const override    { return ObjectSpec::GetByTile(index)->grf_prop.grffile == nullptr; }
 	bool ShowSpriteDumpButton(uint index) const override { return true; }
 	uint GetParent(uint index) const override            { return GetInspectWindowNumber(GSF_FAKE_TOWNS, Object::GetByTile(index)->town->index); }
 	const void *GetInstance(uint index)const override    { return Object::GetByTile(index); }
 	const void *GetSpec(uint index) const override       { return ObjectSpec::GetByTile(index); }
 	void SetStringParameters(uint index) const override  { this->SetObjectAtStringParameters(STR_NEWGRF_INSPECT_CAPTION_OBJECT_AT_OBJECT, INVALID_STRING_ID, index); }
-	uint32 GetGRFID(uint index) const override           { return (this->IsInspectable(index)) ? ObjectSpec::GetByTile(index)->grf_prop.grffile->grfid : 0; }
+	uint32 GetGRFID(uint index) const override           { return (!this->ShowExtraInfoOnly(index)) ? ObjectSpec::GetByTile(index)->grf_prop.grffile->grfid : 0; }
 
 	uint Resolve(uint index, uint var, uint param, GetVariableExtra *extra) const override
 	{
@@ -1312,8 +1313,11 @@ class NIHObject : public NIHelper {
 		if (spec) {
 			ObjectID id = GetObjectIndex(index);
 			const Object *obj = Object::Get(id);
-			uint class_id = ObjectClass::Get(spec->cls_id)->global_id;
-			seprintf(buffer, lastof(buffer), "  index: %u, type ID: %u, class ID: %c%c%c%c", id, GetObjectType(index), class_id >> 24, class_id >> 16, class_id >> 8, class_id);
+			char *b = buffer + seprintf(buffer, lastof(buffer), "  index: %u, type ID: %u", id, GetObjectType(index));
+			if (spec->cls_id != INVALID_OBJECT_CLASS) {
+				uint class_id = ObjectClass::Get(spec->cls_id)->global_id;
+				b += seprintf(b, lastof(buffer), ", class ID: %c%c%c%c", class_id >> 24, class_id >> 16, class_id >> 8, class_id);
+			}
 			output.print(buffer);
 			seprintf(buffer, lastof(buffer), "  view: %u, colour: %u, effective foundation: %u", obj->view, obj->colour, GetObjectEffectiveFoundationType(index));
 			output.print(buffer);