Allowed to name property with a name that already exists -> overwrites the existing property

Steps to reproduce:

• Create/open a project
• Add rectangle from Components to 2D view
• Add new property for rectangle from Properties -> User added properties -> +
• select type string and give a name width
• -> does not warn about property already existing, in code editor width property gets value ""

    Rectangle {
        id: rectangle1
        x: 566
        y: 334
        width: ""
        height: 200
        color: "#ffffff"

• Change the original width property value to 300 in Properties -> Geometry - 2D -> Size W
• Click in 2D view
• Select rectangle1 again in 2D or Navigator
• -> new added property is gone from user added properties