Don't panic in trie_error_val_index either

components/collections/src/codepointtrie/cptrie.rs

@@ -236,7 +236,11 @@ impl<'trie, T: TrieValue> CodePointTrie<'trie, T> {
     /// error value.
     #[inline(always)] // `always` based on normalizer benchmarking
     fn trie_error_val_index(&self) -> u32 {
-        self.data.len() as u32 - ERROR_VALUE_NEG_DATA_OFFSET
+        // We use wrapping_sub here to avoid panicky overflow checks.
+        // len should always be > 1, but if it isn't this will just cause GIGO behavior of producing
+        // None on `.get()`
+        debug_assert!(self.data.len() as u32 >= ERROR_VALUE_NEG_DATA_OFFSET);
+        (self.data.len() as u32).wrapping_sub(ERROR_VALUE_NEG_DATA_OFFSET)
     }
 
     fn internal_small_index(&self, code_point: u32) -> u32 {