Fix the endoffset of the last glyph when it's followed by a null offset in the loca table

It fixes #17671.

src/core/fonts.js

@@ -2117,6 +2117,14 @@ class Font {
         break;
       }
 
+      // If the last offset is 0 in the loca table then we can't compute the
+      // endOffset for the last glyph. So in such a case we set the endOffset
+      // to the end of the data (fixes issue #17671).
+      const last = locaEntries.at(-2);
+      if (last.offset !== 0 && last.endOffset === 0) {
+        last.endOffset = oldGlyfDataLength;
+      }
+
       const missingGlyphs = Object.create(null);
       let writeOffset = 0;
       itemEncode(locaData, 0, writeOffset);

test/pdfs/.gitignore

@@ -628,3 +628,4 @@
 !issue17492.pdf
 !issue17540.pdf
 !bug1669097.pdf
+!issue17671.pdf

test/test_manifest.json

@@ -9675,5 +9675,12 @@
         "id": null
       }
     }
+  },
+  {
+    "id": "issue17671",
+    "file": "pdfs/issue17671.pdf",
+    "md5": "407695b36b4611bc7c501a891c8a4b28",
+    "rounds": 1,
+    "type": "eq"
   }
 ]