Fix condition logic for user signature and null checks

Author: Cyperghost

wcfsetup/install/files/lib/system/condition/type/user/AbstractUserIsNullConditionType.class.php

@@ -16,9 +16,9 @@ abstract class AbstractUserIsNullConditionType extends AbstractUserBooleanCondit
     public function applyFilter(DatabaseObjectList $objectList): void
     {
         if ($this->filter) {
-            $objectList->getConditionBuilder()->add("{$objectList->getDatabaseTableAlias()}.{$this->columnName} IS NULL");
-        } else {
             $objectList->getConditionBuilder()->add("{$objectList->getDatabaseTableAlias()}.{$this->columnName} IS NOT NULL");
+        } else {
+            $objectList->getConditionBuilder()->add("{$objectList->getDatabaseTableAlias()}.{$this->columnName} IS NULL");
         }
     }
 

wcfsetup/install/files/lib/system/condition/type/user/UserSignatureConditionType.class.php

@@ -22,12 +22,12 @@ public function applyFilter(DatabaseObjectList $objectList): void
     {
         if ($this->filter) {
             $objectList->getConditionBuilder()->add(
-                "({$objectList->getDatabaseTableAlias()}.signature = ? OR {$objectList->getDatabaseTableAlias()}.signature IS NULL)",
+                "({$objectList->getDatabaseTableAlias()}.signature <> ? AND {$objectList->getDatabaseTableAlias()}.signature IS NOT NULL)",
                 ['']
             );
         } else {
             $objectList->getConditionBuilder()->add(
-                "({$objectList->getDatabaseTableAlias()}.signature <> ? AND {$objectList->getDatabaseTableAlias()}.signature IS NOT NULL)",
+                "({$objectList->getDatabaseTableAlias()}.signature = ? OR {$objectList->getDatabaseTableAlias()}.signature IS NULL)",
                 ['']
             );
         }