Steps to reproduce:

1. Install Crowd (make sure that this is a fresh installation, existing installation does not have the error)
2. Add an application into Crowd
3. Fresh installation does not have SSO domain value in Crowd General Option (Do not click Update in Crowd General Options page so that it will not update SSO domain with empty string too)
4. Enable SSO plugin in Stash
5. Add Crowd directory into Stash
6. Logout from your current Stash internal user
7. NPE happen in all Stash pages

   java.lang.NullPointerException
   	java.lang.String.endsWith(String.java:1465)
   	com.atlassian.stash.plugin.auth.crowd.internal.DefaultCrowdSsoService.isSsoDomain(DefaultCrowdSsoService.java:103)
   	com.atlassian.stash.plugin.auth.crowd.internal.CrowdSsoAuthenticationHandler.authenticate(CrowdSsoAuthenticationHandler.java:70)
   	com.atlassian.stash.internal.spring.security.PluginAuthenticationProvider$1.perform(PluginAuthenticationProvider.java:94)
   	com.atlassian.stash.internal.spring.security.PluginAuthenticationProvider$1.perform(PluginAuthenticationProvider.java:91)
   	com.atlassian.stash.internal.spring.security.PluginAuthenticationProvider.attemptAuthentication(PluginAuthenticationProvider.java:104)
   	com.atlassian.stash.internal.spring.security.PluginAuthenticationProvider.authenticate(PluginAuthenticationProvider.java:57)
   	sun.reflect.GeneratedMethodAccessor272.invoke(Unknown Source)
   	sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
   	java.lang.reflect.Method.invoke(Method.java:597)
   	org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:317)
   	org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:183)