frontend: Prevent sending an empty version when fetching instances

Sending an empty version is not allowed in the current API. That
should be ideally prevented in the backend, but until then, this
patch removes an empty version from the query params in the
respective API call.

frontend/src/api/API.ts

@@ -195,12 +195,19 @@ export default class API {
   static getInstances(
     applicationID: string,
     groupID: string,
-    queryOptions = {}
+    queryOptions: {
+      [key: string]: any;
+    } = {}
   ): Promise<Instances> {
     let url = BASE_URL + '/apps/' + applicationID + '/groups/' + groupID + '/instances';
 
     if (!_.isEmpty(queryOptions)) {
-      url += '?' + queryString.stringify(queryOptions);
+      let sanitizedOptions = queryOptions;
+      const { version, ...otherOptions } = queryOptions;
+      if (!version) {
+        sanitizedOptions = otherOptions;
+      }
+      url += '?' + queryString.stringify(sanitizedOptions);
     }
 
     return API.getJSON(url);