Catch errors when calculating avg font width (#43503)

When calculating the avg width it's possible for `fontkit` to throw if it can't get the width of the glyphs for a font file. In that case skip the `size-adjust` property and use the other overrides.

#41745 (comment) here's an example of an error thrown by fontkit.

## Bug

- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have a helpful link attached, see [`contributing.md`](https://github.com/vercel/next.js/blob/canary/contributing.md)

## Feature

- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [ ] [e2e](https://github.com/vercel/next.js/blob/canary/contributing/core/testing.md#writing-tests-for-nextjs) tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have a helpful link attached, see [`contributing.md`](https://github.com/vercel/next.js/blob/canary/contributing.md)

## Documentation / Examples

- [ ] Make sure the linting passes by running `pnpm build && pnpm lint`
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packages/font/src/utils.ts

@@ -13,19 +13,24 @@ const DEFAULT_SERIF_FONT = {
 }
 
 function calcAverageWidth(font: Font): number | undefined {
-  const avgCharacters = 'aaabcdeeeefghiijklmnnoopqrrssttuvwxyz      '
-  const hasAllChars = font
-    .glyphsForString(avgCharacters)
-    .flatMap((glyph) => glyph.codePoints)
-    .every((codePoint) => font.hasGlyphForCodePoint(codePoint))
-
-  if (!hasAllChars) return undefined
-
-  const widths = font
-    .glyphsForString(avgCharacters)
-    .map((glyph) => glyph.advanceWidth)
-  const totalWidth = widths.reduce((sum, width) => sum + width, 0)
-  return totalWidth / widths.length
+  try {
+    const avgCharacters = 'aaabcdeeeefghiijklmnnoopqrrssttuvwxyz      '
+    const hasAllChars = font
+      .glyphsForString(avgCharacters)
+      .flatMap((glyph) => glyph.codePoints)
+      .every((codePoint) => font.hasGlyphForCodePoint(codePoint))
+
+    if (!hasAllChars) return undefined
+
+    const widths = font
+      .glyphsForString(avgCharacters)
+      .map((glyph) => glyph.advanceWidth)
+    const totalWidth = widths.reduce((sum, width) => sum + width, 0)
+    return totalWidth / widths.length
+  } catch {
+    // Could not calculate average width from the font file, skip size-adjust
+    return undefined
+  }
 }
 
 function formatOverrideValue(val: number) {