Negative estimated hours should not be valid (#12735).

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11125 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/models/issue.rb

@@ -67,7 +67,7 @@ class Issue < ActiveRecord::Base
 
   validates_length_of :subject, :maximum => 255
   validates_inclusion_of :done_ratio, :in => 0..100
-  validates_numericality_of :estimated_hours, :allow_nil => true
+  validates :estimated_hours, :numericality => {:greater_than_or_equal_to => 0, :allow_nil => true, :message => :invalid}
   validates :start_date, :date => true
   validates :due_date, :date => true
   validate :validate_issue, :validate_required_fields