Fixed crash when html file is empty and when canvas fails to aprse

Nuake/src/UI/Inspector.h

@@ -96,6 +96,11 @@ namespace NuakeUI
 
 	static void DrawInspector(std::shared_ptr<Canvas> canvas)
 	{
+		if (canvas == nullptr)
+		{
+			return;
+		}
+
 		if (ImGui::Begin("Inspector"))
 		{
 			if (ImGui::BeginTabBar("MyTabBar"))

Nuake/src/UI/Nodes/Canvas.cpp

@@ -55,15 +55,11 @@ namespace NuakeUI
 	
 	void Canvas::ComputeLayout(Vector2 size)
 	{
-		if (!mRootNode)
+		if (!mRootNode || mInputManager)
 			return;
 		
 		Renderer::Get().SetViewportSize(size);
 
-		float x, y;
-		x = mInputManager->GetMouseX();
-		y = mInputManager->GetMouseY();
-
 		auto root = mRootNode->GetYogaNode();
 
 		// Recompute the node tree.