fix printing of TryStatement

I'm opening this PR to show what I had to do to fix this, but I'm not recommending it be merged. I don't know how to handle the `handlers` array, but this makes it work with a single handler.

With the previous code, I get this error:

```
assert.js:92
  throw new assert.AssertionError({
        ^
AssertionError: false == true
    at printWithComments (/Users/james/projects/regenerator/node_modules/recast/lib/prin
ter.js:65:14)                                                                          
    at /Users/james/projects/regenerator/node_modules/recast/lib/printer.js:681:29
    at Array.forEach (native)
    at genericPrintNoParens (/Users/james/projects/regenerator/node_modules/recast/lib/p
rinter.js:679:20)                                                                      
```

with this AST:

```
    b.tryStatement(
      b.blockStatement(machine.ast),
      b.catchClause(b.identifier('e'), null, b.blockStatement([
        b.expressionStatement(
          b.assignmentExpression(
            '=',
            b.memberExpression(b.identifier('$ctx'), b.identifier('errored'), false),
            b.literal(true)
          )
        )
      ]))
    )
```