Rectangular artifacts flicker around the cursor in the Scene view when the Aspect Brush Mask Filter is added to Terrain brush

Reproduction steps:
1. Create a new project
2. Install Terrain Tools package (Window > Package Management > Package Manager)
3. GameObject > 3D Object > Terrain
4. Select the Terrain in the Hierarchy and select Paint Terrain Tool in the Inspector
5. Press the "+" button in the Brush Mask > Brush Mask Filters section and select "Aspect"
6. Move the mouse cursor around the Terrain in the Scene view and observe

Actual result: Black rectangular artifact is flickering around the cursor while the cursor is moved over the Terrain
Expected result: No flickering artefacts are rendered in the Scene view

Reproducible with: 5.1.0 (6000.0.0f1), 5.3.3 (6000.7.0a5)

Reproduced on: macOS Tahoe 26.6 (M4)