Travis fails on Electron builds using Node 12.x

The error is:
```
Error: No test files found
The command "if [[ "${NODE_VERSION}" ]]; then if [[ "${ELECTRON_VERSION}" ]]; then ./scripts/build_against_electron.sh; else ./scripts/build_against_node.sh; fi; fi" exited with 1.
```

This seems to affect all new PRs, such as #1192 & #1195

Here is a failing Travis job: https://travis-ci.org/mapbox/node-sqlite3/jobs/565236851