Add null check in React sample to catch if loginResponse is null, fixes #1021
Add null check in React sample to catch if loginResponse is null, fixes #1021

AzureAD/microsoft-authentication-library-for-js,AzureAD/microsoft-authentication-library-for-js,AzureAD/microsoft-authentication-library-for-js,AzureAD/microsoft-authentication-library-for-js,AzureAD/microsoft-authentication-library-for-js,AzureAD/microsoft-authentication-library-for-js,AzureAD/microsoft-authentication-library-for-js,AzureAD/microsoft-authentication-library-for-js