Return false for empty file.

lib/linguist/generated.rb

@@ -281,6 +281,7 @@ module Linguist
     # Return true or false
     def compiled_cython_file?
       return false unless ['.c', '.cpp'].include? extname
+      return false unless lines.count > 1
       return lines[0].include?("Generated by Cython")
     end
   end