parse.y: Fix the locations of an empty script

* parse.y: Fix the locations of NODE_BEGIN in
  an empty script.

  ```
  ruby --dump=p -e ''
  ```

  * Before

  ```
  NODE_BEGIN (line: 1, code_range: (1,1)-(1,1))
  ```

  * After

  ```
  NODE_BEGIN (line: 1, code_range: (1,0)-(1,0))
  ```

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61196 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

parse.y

@@ -1205,7 +1205,7 @@ top_compstmt	: top_stmts opt_terms
 top_stmts	: none
                     {
 		    /*%%%*/
-			$$ = new_begin(0, &@$);
+			$$ = new_begin(0, &@0);
 		    /*%
 			$$ = dispatch2(stmts_add, dispatch0(stmts_new),
 						  dispatch0(void_stmt));