Need help solving unserialize():Error at offset
This line reads the data from the table civicrm_setting and specifically the column value.  You could use a SQL client to run the query:

SELECT id, name, value FROM civicrm_setting;


Typical values would look these:


NULL
i:0; (an integer)
b:1; (a boolean?)
s:20:"CRM/common/fatal.tpl"; (a string)
a:1:{s:3:"key";s:5:"value";} (an array or dictionary)


Skim them and see if one of the values looks to have a different/unexpected format.



(UPDATE) Seamus Lee pointed me to https://www.drupal.org/node/1114304 which uses a clever technique for finding badly serialized data. Take the error message (Error at offset 0 of 8 bytes) and note the length (8 bytes). Search on that:

SELECT id, name, value FROM civicrm_setting WHERE length(value) = 8;