Bug 3202: creating new 'child' categorytype patrons doesn't set branch properly

Bug 3202: creating new 'child' categorytype patrons doesn't set branch properly

If a guarantor search is not being performed, the creation of any Child category_type patron will
not default to the currently logged in branch, but rather the first branch alphabetically.

Adding a test for the existence of any guarantor branch data before assigning it clears up this problem

Signed-off-by: Nicole C. Engard <nengard@bywatersolutions.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>