Don't blow up if empty string/nil passed to alias methods

lib/linguist/language.rb

@@ -150,6 +150,7 @@ module Linguist
     #
     # Returns the Language or nil if none was found.
     def self.find_by_name(name)
+      return nil if name.to_s.empty?
       name && (@name_index[name.downcase] || @name_index[name.split(',').first.downcase])
     end
 
@@ -164,6 +165,7 @@ module Linguist
     #
     # Returns the Language or nil if none was found.
     def self.find_by_alias(name)
+      return nil if name.to_s.empty?
       name && (@alias_index[name.downcase] || @alias_index[name.split(',').first.downcase])
     end
 

test/test_language.rb

@@ -275,6 +275,11 @@ class TestLanguage < Minitest::Test
     assert_equal Language['Rust'], Language.find_by_alias('rust,no_run')
   end
 
+  def test_doesnt_blow_up_with_blank_lookup
+    assert_equal nil, Language.find_by_alias('')
+    assert_equal nil, Language.find_by_name(nil)
+  end
+
   def test_name
     assert_equal 'Perl',   Language['Perl'].name
     assert_equal 'Python', Language['Python'].name