BUG: unnecessary check if user exists removed

src/main/java/caosdb/server/accessControl/Pam.java

@@ -24,7 +24,6 @@
  */
 package caosdb.server.accessControl;
 
-import caosdb.server.caching.Cache;
 import java.io.File;
 import java.io.IOException;
 import java.util.HashSet;
@@ -37,6 +36,7 @@ import org.apache.logging.log4j.Logger;
 import org.apache.shiro.authz.AuthorizationException;
 import org.jvnet.libpam.PAMException;
 import org.jvnet.libpam.UnixUser;
+import caosdb.server.caching.Cache;
 
 /**
  * PAM UserSource for authenticating users via the Host's pam module.
@@ -260,7 +260,7 @@ public class Pam implements UserSource {
   /** @see {@link UserSource#isValid(String, String)}. */
   @Override
   public boolean isValid(final String username, final String password) {
-    if (isUserExisting(username)) {
+    if (username != null && isIncorporated(username)) {
       return isValid(getPamScriptCaller(), username, password);
     }
     return false;