buffer: add assert.fail()

Author: haramj

lib/buffer.js

@@ -99,6 +99,8 @@ const {
   inspect: utilInspect,
 } = require('internal/util/inspect');
 
+const assert = require('internal/assert');
+
 const {
   codes: {
     ERR_BUFFER_OUT_OF_BOUNDS,
@@ -1302,6 +1304,8 @@ function atob(input) {
       throw lazyDOMException(
         'The string to be decoded is not correctly encoded.',
         'InvalidCharacterError');
+    case -3:
+      assert.fail('Unrecognized simdutf error');
     default:
       return result;
   }