Version: allow comparing against nil

Library/Homebrew/test/test_versions.rb

@@ -145,6 +145,10 @@ class VersionComparisonTests < Homebrew::TestCase
     assert_operator version("2-p194"), :<, version("2.1-p195")
   end
 
+  def test_comparing_against_nil
+    assert_operator version("2.1.0-p194"), :>, nil
+  end
+
   def test_comparison_returns_nil_for_non_version
     v = version("1.0")
     assert_nil v <=> Object.new

Library/Homebrew/version.rb

@@ -213,6 +213,8 @@ class Version
   end
 
   def <=>(other)
+    return 1 if other.nil?
+
     return unless other.is_a?(Version)
     return 0 if version == other.version
     return 1 if head? && !other.head?