Empty ImageViewer and Label controls are invisible in the web page designer

In Objo Studio's web page designer, an ImageViewer with no image asset and a Label with blank text are completely invisible on the design surface. The only cue is the blue selection outline while the control happens to be selected; click anywhere else and the control disappears entirely, with no indication that the area of the page is occupied.

The desktop Window designer already handles both cases: an empty Label shows a dashed placeholder rectangle, and an empty ImageViewer shows a filled placeholder with an image icon and caption. The web page designer should match this behaviour so empty controls always remain visible on the canvas.