Crash when editing text after importing `.asketch` file
Tried using this project to experiment both with a fork of https://github.com/brainly/html-sketchapp-example/ and [this branch of seek-style-guide](https://github.com/seek-oss/seek-style-guide/tree/generate-sketch-symbols-with-html-sketchapp).

For both those projects, I was able to reproduce crashes with these steps:

1. Import an `asketch` file with some text values
2. Try to either edit a generated text layer or a new text layer
3. Sketch crashes

Was able to reproduce in both Sketch stable and beta.

### Sketch Stable (47.1) Error Log
[Error log linked in this gist](https://gist.github.com/ryngonzalez/7e5f9a6c3206235d0a7c1f1f979eb26d)

### Sketch Beta (48) Error Log
[Error log linked in this gist](https://gist.github.com/ryngonzalez/d1a88c8283ecc388bfe6d81661353092)