If input or output PortWidgets do not exist when adding a CableWidget, delete the CableWidget and remove Cable from Engine.

src/app/CableWidget.cpp

@@ -166,17 +166,22 @@ void CableWidget::setCable(engine::Cable* cable) {
 		delete this->cable;
 		this->cable = NULL;
 	}
-	this->cable = cable;
 	if (cable) {
-		app::ModuleWidget* outputModule = APP->scene->rack->getModule(cable->outputModule->id);
-		assert(outputModule);
-		outputPort = outputModule->getOutput(cable->outputId);
-		assert(outputPort);
-
-		app::ModuleWidget* inputModule = APP->scene->rack->getModule(cable->inputModule->id);
-		assert(inputModule);
-		inputPort = inputModule->getInput(cable->inputId);
-		assert(inputPort);
+		app::ModuleWidget* outputMw = APP->scene->rack->getModule(cable->outputModule->id);
+		if (!outputMw)
+			throw Exception("Cable cannot find output ModuleWidget %lld", cable->outputModule->id);
+		outputPort = outputMw->getOutput(cable->outputId);
+		if (!outputPort)
+			throw Exception("Cable cannot find output port %d", cable->outputId);
+
+		app::ModuleWidget* inputMw = APP->scene->rack->getModule(cable->inputModule->id);
+		if (!inputMw)
+			throw Exception("Cable cannot find input ModuleWidget %lld", cable->inputModule->id);
+		inputPort = inputMw->getInput(cable->inputId);
+		if (!inputPort)
+			throw Exception("Cable cannot find input port %d", cable->inputId);
+
+		this->cable = cable;
 	}
 	else {
 		outputPort = NULL;

src/app/RackWidget.cpp

@@ -395,6 +395,7 @@ void RackWidget::fromJson(json_t* rootJ) {
 		// Get cable ID
 		json_t* idJ = json_object_get(cableJ, "id");
 		int64_t id;
+		// In <=v0.6, the cable ID was the index in the array.
 		if (idJ)
 			id = json_integer_value(idJ);
 		else
@@ -409,11 +410,20 @@ void RackWidget::fromJson(json_t* rootJ) {
 
 		// Create CableWidget
 		CableWidget* cw = new CableWidget;
-		cw->setCable(cable);
-		cw->fromJson(cableJ);
-		// In <=v1, cable colors were not serialized, so choose one from the available colors.
-		if (cw->color.a == 0.f) {
-			cw->color = getNextCableColor();
+		try {
+			cw->setCable(cable);
+			cw->fromJson(cableJ);
+			// In <=v1, cable colors were not serialized, so choose one from the available colors.
+			if (cw->color.a == 0.f) {
+				cw->color = getNextCableColor();
+			}
+		}
+		catch (Exception& e) {
+			delete cw;
+			// If creating CableWidget fails, remove Cable from Engine.
+			APP->engine->removeCable(cable);
+			delete cable;
+			continue;
 		}
 		addCable(cw);
 	}