TypeError when running eos-transfers example

When running the unmodified eos-transfers example, after a while I get the following error:
```
{"name":"demux","hostname":"Ubuntu-1804-bionic-64-minimal","pid":30211,"level":30,"msg":"Rolling back 1 blocks to block 7986487...","time":"2019-01-10T05:07:43.811Z","v":0}
(node:30211) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'indexState' of undefined
at ObjectActionHandler.loadIndexState (/home/demo/demux-js/examples/eos-transfers/ObjectActionHandler.js:56:18)
at ObjectActionHandler. (/home/demo/demux-js/examples/eos-transfers/node_modules/demux/dist/AbstractActionHandler.js:165:79)
at Generator.next ()
at /home/demo/demux-js/examples/eos-transfers/node_modules/demux/dist/AbstractActionHandler.js:7:71
at new Promise ()
at __awaiter (/home/demo/demux-js/examples/eos-transfers/node_modules/demux/dist/AbstractActionHandler.js:3:12)
at ObjectActionHandler.refreshIndexState (/home/demo/demux-js/examples/eos-transfers/node_modules/demux/dist/AbstractActionHandler.js:164:16)
at ObjectActionHandler. (/home/demo/demux-js/examples/eos-transfers/node_modules/demux/dist/AbstractActionHandler.js:50:28)
at Generator.next ()
at fulfilled (/home/demo/demux-js/examples/eos-transfers/node_modules/demux/dist/AbstractActionHandler.js:4:58)
(node:30211) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 4)
(node:30211) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
```

I suspect it has something to do with fork handling because it usually comes immediately after a fork has been handled, but not always. Sometimes it handles a dozen forks fine and then suddenly, the error pops up.

The Jungle testnet seems to have conditions that provoke this error more often than then mainnet.

Run the unmodified examples/eos-transfers example against the Jungle testnet and observe behavior around fork handling. Inspect examples/eos-transfers/ObjectActionHandler.js at line 56 and the AbstractActionHandler stack shown in the report. Done means fork processing no longer produces the indexState TypeError or an unhandled promise rejection.

Written by the indexing model from the issue text.