Insert null email as DEFAULT so column default may take effect

Ugly implementation to fit into AuthMe 5.4. If email on PlayerAuth is null, do not supply NULL as the email value but use DEFAULT instead so that the default value is used if present in the column configuration.

src/main/java/fr/xephi/authme/security/crypts/PhpBB.java

@@ -147,10 +147,7 @@ public class PhpBB implements EncryptionMethod {
         }
 
         private static boolean phpbb_check_hash(String password, String hash) {
-            if (hash.length() == 34) {
-                return _hash_crypt_private(password, hash).equals(hash);
-            }
-            return md5(password).equals(hash);
+            return _hash_crypt_private(password, hash).equals(hash);
         }
     }
 }