fix(unpersistModel) Add default value for opts param

Just an empty object, so looking up a property on it doesn't error.
(Also some whitespace changes that automatically changed on save.)

src/flux/stores/database-store.es6

@@ -812,7 +812,7 @@ class DatabaseStore extends NylasStore {
 
   // opts can have a boolean isBeingUnpersisted value, which when true prevents
   // this function from re-persisting the model.
-  unindexModel(model, opts) {
+  unindexModel(model, opts = {}) {
     const searchTableName = `${model.constructor.name}Search`;
     const sql = (
       `DELETE FROM \`${searchTableName}\` WHERE \`${searchTableName}\`.\`content_id\` = ?`