Just a brief note here for any lost souls on the search for information.

I recently updated my Piwigo and added a new version of a plugin via the CLI (big mistake, apparently?). I deleted the old folder (‘stripped’) and unzipped the new one with the same name.

On loading up Piwigo, i got:

Warning: Smarty error: unable to read resource: "index.tpl" in /var/www/piwigo/include/smarty/libs/Smarty.class.php

Amongst a whole raft of other rubbish – meaning i couldnt access the database.  I tried deleting it, same issue, and even got into the administration window and changed the default theme; same issue.

Turns out what you need to do is drop that particular row from the database / table as below:

[root@rhelserver piwigo2]# mysql -u root -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 9973
Server version: 5.1.69 Source distribution

Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

 mysql> use piwigo;

Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed

mysql> select * from piwigo_themes;
+---------------------+---------+------------------------+
| id | version | name |
+---------------------+---------+------------------------+
| clear | 2.3.0 | clear |
| dark | 2.3.0 | dark |
| elegant | 2.3.0 | elegant |
| smartpocket | 2.4.0 | Smart Pocket |
| Sylvia | 2.3.0 | Sylvia |
| Full_Background | 2.3 | Full_Background |
| stripped_black_bloc | 2.6.3 | Stripped & Columns |
| simple | 4.1.2 | Simple Grey |
+---------------------+---------+------------------------+
8 rows in set (0.00 sec)

mysql> DELETE FROM piwigo_themes WHERE id="stripped_black_bloc";
Query OK, 1 row affected (0.00 sec)

mysql> select * from piwigo_themes;
+-----------------+---------+-----------------+
| id | version | name |
+-----------------+---------+-----------------+
| clear | 2.3.0 | clear |
| dark | 2.3.0 | dark |
| elegant | 2.3.0 | elegant |
| smartpocket | 2.4.0 | Smart Pocket |
| Sylvia | 2.3.0 | Sylvia |
| Full_Background | 2.3 | Full_Background |
| simple | 4.1.2 | Simple Grey |
+-----------------+---------+-----------------+
7 rows in set (0.00 sec)

mysql> exit;

Bye

Then navigate to your Piwigo server and voila, it works. Huzzah.