babel-ts crashes on `(a:b)`
**Prettier 2.0.4**
[Playground link](https://prettier.io/playground/#N4Igxg9gdgLgprEAuEAKAhkgRgShAGhAgAcYBLaAZ2VHQCc6IB3ABXoWpXQBsn0BPaoSx10YANZwYAZWJiyUAObIYdAK5xCACxgBbbgHUtZeJTlg40jibIA3E-2ThKQkAspw6MFqMW70yABmPB6EAFaUAB4AQqISUtLounAAMgpwQSGaIBGR0gqK3HAAimoQ8JncoSBydB50TljoWHDcALQwrsR0CjAGZAAmMFrIABwADITdEB4GosRO3XD1thmEAI5l8D4knCDolG1QcHADpwQgdHCbZFc+6H4BSMFV2R66ZCrqbwVFpeUZZ5ZQgwZr9IYjJAAJhBojI3AKAGEILp-E5lgBWC5qDwAFWanBe1VsGgAklAzrBpGAeqQAIIU6QwfhFSoeAC+7KAA)
```sh
--parser babel-ts
```

**Input:**
```tsx
(a:b)
```

**Output:**
```tsx
printPathNoParens@https://prettier.io/lib/standalone.js:28544:15
genericPrint$3@https://prettier.io/lib/standalone.js:26180:49
callPluginPrintFunction@https://prettier.io/lib/standalone.js:16919:20
printGenerically/res<@https://prettier.io/lib/standalone.js:16869:72
printComments@https://prettier.io/lib/standalone.js:16542:26
printGenerically@https://prettier.io/lib/standalone.js:16869:24
call@https://prettier.io/lib/standalone.js:16662:30
printPathNoParens@https://prettier.io/lib/standalone.js:26439:31
genericPrint$3@https://prettier.io/lib/standalone.js:26180:49
callPluginPrintFunction@https://prettier.io/lib/standalone.js:16919:20
printGenerically/res<@https://prettier.io/lib/standalone.js:16869:72
printComments@https://prettier.io/lib/standalone.js:16542:26
printGenerically@https://prettier.io/lib/standalone.js:16869:24
printStatementSequence/<@https://prettier.io/lib/standalone.js:28568:32
map@https://prettier.io/lib/standalone.js:16728:23
printStatementSequence@https://prettier.io/lib/standalone.js:28552:10
printPathNoParens/<@https://prettier.io/lib/standalone.js:26406:18
call@https://prettier.io/lib/standalone.js:16662:30
printPathNoParens@https://prettier.io/lib/standalone.js:26405:25
genericPrint$3@https://prettier.io/lib/standalone.js:26180:49
callPluginPrintFunction@https://prettier.io/lib/standalone.js:16919:20
printGenerically/res<@https://prettier.io/lib/standalone.js:16869:72
printComments@https://prettier.io/lib/standalone.js:16542:26
printGenerically@https://prettier.io/lib/standalone.js:16869:24
call@https://prettier.io/lib/standalone.js:16662:30
printPathNoParens@https://prettier.io/lib/standalone.js:26390:25
genericPrint$3@https://prettier.io/lib/standalone.js:26180:49
callPluginPrintFunction@https://prettier.io/lib/standalone.js:16919:20
printGenerically/res<@https://prettier.io/lib/standalone.js:16869:72
printComments@https://prettier.io/lib/standalone.js:16542:26
printGenerically@https://prettier.io/lib/standalone.js:16869:24
printAstToDoc@https://prettier.io/lib/standalone.js:16879:31
coreFormat@https://prettier.io/lib/standalone.js:17147:25
format@https://prettier.io/lib/standalone.js:17367:77
formatWithCursor@https://prettier.io/lib/standalone.js:17383:14
withPlugins/<@https://prettier.io/lib/standalone.js:32885:14
format@https://prettier.io/lib/standalone.js:32894:14
formatCode@https://prettier.io/worker.js:233:21
handleMessage@https://prettier.io/worker.js:184:18
self.onmessage@https://prettier.io/worker.js:154:14
EventHandlerNonNull*@https://prettier.io/worker.js:151:1

```

**Expected behavior:**
Print a regular parse error message.