Use try instead of safe navigation operator on possible undefined att…

…ribute

Since the safe navigation operator does raise on undefined methods we should use try instead.

app/models/spree/user_decorator.rb

@@ -5,7 +5,7 @@ def self.prepended(base)
   end
 
   def ensure_mollie_customer
-    return if mollie_customer_id&.present?
+    return if try(:mollie_customer_id).present?
 
     # Don't create Mollie customers if spree_auth_devise is not installed.
     return unless defined? Spree::User