Fixes issues with user and team picker

public/app/core/components/Select/TeamPicker.tsx

 import React, { Component } from 'react';
+import _ from 'lodash';
 import { AsyncSelect } from './Select';
 import { debounce } from 'lodash';
 import { getBackendSrv } from 'app/core/services/backend_srv';
@@ -37,6 +38,10 @@ export class TeamPicker extends Component<Props, State> {
     const backendSrv = getBackendSrv();
     this.setState({ isLoading: true });
 
+    if (_.isNil(query)) {
+      query = '';
+    }
+
     return backendSrv.get(`/api/teams/search?perpage=10&page=1&query=${query}`).then(result => {
       const teams = result.teams.map(team => {
         return {

public/app/core/components/Select/UserPicker.tsx

 // Libraries
 import React, { Component } from 'react';
+import _ from 'lodash';
 
 // Components
 import { AsyncSelect } from './Select';
@@ -38,6 +39,10 @@ export class UserPicker extends Component<Props, State> {
     const backendSrv = getBackendSrv();
     this.setState({ isLoading: true });
 
+    if (_.isNil(query)) {
+      query = '';
+    }
+
     return backendSrv
       .get(`/api/org/users?query=${query}&limit=10`)
       .then(result => {