Merge branch 'hotfix/1.3.13'
Starting 1.3.14 hotfix branch
Fixed potential warning in rules when user has no groups
Fixed potential exception when passing invalid data to the URL

see https://community.contao.org/de/showthread.php?37668-Produktleser-per-Ajax-updaten&p=243991#post243991
Incorrect rounding for product discount on cart subtotal rules
Products in cart limit was not applied for product rules
Fix foreach error when no options are available (#541)
Fixed error in IsotopeEmail class when passing an array of recipients
Finishing 1.3.14 hotfix branch
Merge branch 'hotfix/1.3.14' into release/1.4.0