IndexOutOfRangeException is thrown continuously when selecting an older TMP_Font Asset with an out-of-bounds m_AtlasRenderMode value

How to reproduce:

1. Open the attached “IN-149707_Font Bug.zip” project
2. Navigate to “Assets/TextMeshPro Fonts/Resources/Fonts & Materials/Fonts”
3. Select the font asset "RAYSHAND SDF"
4. Observe the Console
5. Hover the mouse over the Inspector
6. Observe the Console

Actual result: The Console continuously spams "IndexOutOfRangeException: Index was outside the bounds of the array"
Expected result: The Inspector does not throw unhandled exceptions

Reproducible with: 6000.0.80f1, 6000.2.0b2 (2bdac9ac0d74), 6000.3.22f1, 6000.5.8f1, 6000.6.0b8, 6000.7.0a4
Not reproducible with: 6000.0.0f1, 6000.2.0b1 (d17678da8412)

Reproducible on: Windows 11, macOS 26.3.1 (by user)
Not reproducible on: No other environments tested

Workarounds:

• Switch the Inspector to Debug mode (via the three vertical dots ⋮ in the top right)
• Locate the "Atlas Render Mode" property, and set it to any valid value in the Inspector in the Debug mode

Note: The errors multiply rapidly when hovering the mouse over the Inspector due to UI repaints