Recoverable fatal error: Object of class BeanCustom could not be converted to string in DatabaseStatementBase->execute()

Problem/Motivation

Recoverable fatal error is thrown when auto_nodequque passes an object as an argument (type) into DatabaseStatementBase->execute().

Proposed resolution

Check to ensure a string value is passed as an argument after retrieving the queue type value from the form. With BEAN, the value from the form is an object. This is passed as an argument (type) and it causes DatabaseStatementBase->execute() to fail. There might be other cases where you want to check the object for it's type and use that value instead. For the BEAN case, that isn't useful since BEANs can't be part of a nodequeue.

Remaining tasks

1. Post patch.
2. Verify and test patch.
3. Merge patch with 2.x dev branch.

User interface changes

None.

API changes

None.