Store an error node when restarting the parser

FIX: The parser will now emit an error node when it reaches the end of the top rule
but not the end of the input, and restarts parsing the top rule.

See https://discuss.codemirror.net/t/why-does-this-input-generate-no-error/7147

src/stack.ts

@@ -369,6 +369,7 @@ export class Stack {
   /// when this.stack.length == 3 (state is directly below the top
   /// state). @internal
   restart() {
+    this.storeNode(Term.Err, this.pos, this.pos, 4, true)
     this.state = this.stack[0]
     this.stack.length = 0
   }