Fix webServiceUser in SpelContext

Author: LEDfan

src/main/java/eu/openanalytics/containerproxy/spec/expression/SpecExpressionContext.java

@@ -192,7 +192,7 @@ public LdapUserDetails getLdapUser() {
     }
 
     public WebServiceAuthenticationBackend.WebServiceUser getWebServiceUser() {
-        if (oidcUser == null) {
+        if (webServiceUser == null) {
             throw new SpelContextObjectNotAvailableException("webServiceUser");
         }
         return webServiceUser;