Migration script bug: incorrect method called for index.

See this line:

https://code.vtiger.com/vtiger/vtigercrm/blob/master/modules/Migration/schema/660_to_700.php#L1783

You are calling the method Vtiger_Utils::TableHasForeignKey() to check for the presence of an index...

Looking at the method I do not think this is ever going to return true.