If you have a column that has the same name as your table, the original version of this code crashes because you're trying to use the "+" operator to perform a merge of a string to an array. 

Example: 
Table "AccountName"
Fields: 
  - ID
  - AccountNumber
  - AccountName

In this case, the "isset($data[$tableName])" check is true and the code then tries to use the "+" operator to merge a string to the data array. 

This change fixes this since it will only perform the "+" based merge if "$data[$tableName]" is an array