Improved error handling.

app/models/ticket/number/date.rb

@@ -65,6 +65,7 @@ module Ticket::Number::Date
   end
 
   def check(string)
+    return if !string || string.empty?
 
     # get config
     system_id           = Setting.get('system_id') || ''

app/models/ticket/number/increment.rb

@@ -70,6 +70,7 @@ module Ticket::Number::Increment
   end
 
   def check(string)
+    return if !string || string.empty?
 
     # get config
     system_id           = Setting.get('system_id') || ''