Handle some malformed mpd files. Fixes #533.

- Skip duplicate submodels
- Skip recursive includes

common/lc_model.cpp

@@ -734,6 +734,14 @@ void lcModel::LoadLDraw(QIODevice& Device, Project* Project)
 				Piece->SetColorCode(ColorCode);
 				Piece->VerifyControlPoints(ControlPoints);
 				Piece->SetControlPoints(ControlPoints);
+
+				if (Piece->mPieceInfo->IsModel() && Piece->mPieceInfo->GetModel()->IncludesModel(this))
+				{
+					delete Piece;
+					Piece = nullptr;
+					continue;
+				}
+
 				AddPiece(Piece);
 				Piece = nullptr;
 			}

common/project.cpp

@@ -401,9 +401,19 @@ bool Project::Load(const QString& FileName)
 
 			if (Models.empty() || !Model->GetFileName().isEmpty())
 			{
-				mModels.Add(Model);
+				auto ModelCompare = [Model](const std::pair<int, lcModel*>& ModelIt)
-				Models.emplace_back(std::make_pair(Pos, Model));
+				{
-				Model->CreatePieceInfo(this);
+					return ModelIt.second->GetFileName() == Model->GetFileName();
+				};
+
+				if (std::find_if(Models.begin(), Models.end(), ModelCompare) == Models.end())
+				{
+					mModels.Add(Model);
+					Models.emplace_back(std::make_pair(Pos, Model));
+					Model->CreatePieceInfo(this);
+				}
+				else
+					delete Model;
 			}
 			else
 				delete Model;