OO-4008: fix empty string search (patch S. Clemenz)

src/main/java/org/olat/admin/user/UsermanagerUserSearchForm.java

@@ -187,6 +187,8 @@ public class UsermanagerUserSearchForm extends FormBasicController {
 	public SearchIdentityParams getSearchIdentityParams() {
 		// get user attributes from form
 		String idVal = getStringValue("id");
+		idVal = (idVal.equals("") ? null : idVal);
+
 		String loginVal = getStringValue("login");
 		// when searching for deleted users, add wildcard to match with backup prefix
 		List<Integer> statusList = getStatus();

src/main/java/org/olat/basesecurity/manager/IdentityPowerSearchQueriesImpl.java

@@ -543,9 +543,6 @@ public class IdentityPowerSearchQueriesImpl implements IdentityPowerSearchQuerie
 			dbq.setParameter("status", params.getStatus());
 		}
 		
-		if(params.getIdAndExternalIds() != null) {
-		}
-		
 		if(params.getIdAndExternalIds() != null) {
 			if(StringHelper.isLong(params.getIdAndExternalIds())) {
 				dbq.setParameter("idKey", Long.valueOf(params.getIdAndExternalIds()));