People API: Convert null result to an empty array (#633)

* Handle `null` People results

* Improve logic and documentation

* Update person.ts

web/app/serializers/person.ts

@@ -12,14 +12,21 @@ export default class PersonSerializer extends JSONSerializer {
   normalizeResponse(
     _store: DS.Store,
     _primaryModelClass: any,
-    payload: GoogleUser[] | { results: GoogleUser[] },
+    payload: GoogleUser[] | { results: GoogleUser[] | null },
     _id: string | number,
     requestType: string,
   ) {
     const type = "person";
 
     if (requestType === "query") {
       assert("results are expected for query requests", "results" in payload);
+
+      /**
+       * If the results are `null`, return an empty array to show
+       * the "No results found" message in the PeopleSelect.
+       */
+      if (!payload.results) return { data: [] };
+
       const people = payload.results.map((p: any) => {
         return {
           id: p.emailAddresses[0].value,