Fix more of the Fasta tests

pkg/analyzer/lib/src/fasta/ast_builder.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library fasta.analyzer.ast_builder;
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/dart/ast/ast_factory.dart' show AstFactory;
 import 'package:analyzer/dart/ast/standard_ast_factory.dart' as standard;
 import 'package:analyzer/dart/ast/token.dart' show Token, TokenType;
@@ skipping 974 matching lines @@
       if (catchParameters.length > 1) {
         stackTrace = catchParameters[1].identifier;
       }
     }
     push(ast.catchClause(
         onKeyword,
         type,
         catchKeyword,
         catchParameterList?.leftParenthesis,
         exception,
-        null,
+        stackTrace == null ? null : stackTrace.token.previous,
         stackTrace,
         catchParameterList?.rightParenthesis,
         body));
   }
 
   @override
   void handleFinallyBlock(Token finallyKeyword) {
     debugEvent("FinallyBlock");
     // The finally block is popped in "endTryStatement".
   }
@@ skipping 1049 matching lines @@
       } else if (identical('var', s)) {
         finalConstOrVarKeyword = token;
       } else if (identical('covariant', s)) {
         covariantKeyword = token;
       } else {
         unhandled("$s", "modifier", token.charOffset, null);
       }
     }
   }
 }