apparently leaflet.ie isn't a thing any more?

https://github.com/Leaflet/Leaflet/issues/2159

app/assets/stylesheets/application.css

@@ -4,7 +4,6 @@
  * the top of the compiled file, but it's generally better to create a new file per style scope.
  *= require_self
  *= require bootstrap-datepicker
- *= require leaflet.ie
  *= require leaflet
  *= require leaflet.markercluster
  *= require leaflet.markercluster.default