[Bug] Dropdowns are not properly rounded on the corners

[Arrowpuppet]

Step 1. Pre-report Checklist

• I checked if there is already an open issue that described my problem.
• I checked if there is already an open issue at Millennium that describes my problem.
• I ticked the checkboxes without reading them.
• I checked the Update tab to see if there was an update.

Step 2. Theme configuration

Configuration

"Steam": {
      "Add shelf button": "no",
      "Always show download bar": "no",
      "Always show game infos": "no",
      "Always show sidebar": "yes",
      "Banner Infos": "no",
      "Banner position": "Middle (default)",
      "Big Picture Mode button": "no",
      "Bigger banner": "no",
      "Border radius": "8",
      "Broadcast": "no",
      "Darken not installed games": "yes",
      "Digital product info": "no",
      "Dynamic banner height": "no",
      "Follow the creators": "no",
      "Font": "Arial",
      "Footer": "no",
      "Friend icon": "no",
      "Friend list button": "no",
      "Game Overlay": "no",
      "Game cover shiny effect": "no",
      "Game info box artwork": "no",
      "Hide group chat": "no",
      "Info sidebar on right": "no",
      "Landing Header": "no",
      "Max Width": "1200",
      "Mica & Acrylic plugin support": "no",
      "Mica Transparency": "90",
      "Navigation buttons": "no",
      "News button": "no",
      "Notification button": "no",
      "Playbar in Banner": "no",
      "Profile pages header": "no",
      "Recommendations": "no",
      "Scrollbars": "no",
      "Sidebar on left": "no",
      "Sidebar on right": "no",
      "Sidebar only on hover": "no",
      "Steam VR button": "no",
      "Steam-Custom-Artworks Support": "no",
      "System accent colors": "no",
      "URL bar": "no",
      "VAC-Ban visibility": "Show",
      "Wallet balance": "no",
      "What's New": "Compact",
      "Window Controls": "Show",
      "Write a Review": "no"
    }

Step 3. Describe the issue

The borders added to dropdown menus are rounded while the backdrop is not, leaving an overhang from the backdrop which creates these weird looking corners.

Step 4. How to reproduce

1. Hover over anything on the titlebar to show a dropdown menu with the improperly rounded corners.

Anything else?

No response