Applying fix for migrate connection error

See: https://github.com/jh-ism-online-webmaster/Propel/commit/846640a8d00a01c462c3dc78969afa2931e75b54
Merge pull request #851 from exptom/1.7.1-fix

Fix for migrate connection error
Fixed bug introduced by fix [0] and discussed [1].

[0]
https://github.com/propelorm/Propel/commit/dcace442d4dc0302f2db568b0550af73a53532ad

[1]
https://github.com/propelorm/Propel/commit/dcace442d4dc0302f2db568b0550af73a53532ad
Merge pull request #854 from stevleibelt/master

Fixed bug introduced by fix [0] and discussed [1].