resolves #369 don't fail to delete tmp file

lib/asciidoctor-pdf/converter.rb

@@ -2455,8 +2455,9 @@ def resolve_explicit_width attrs, max_width = bounds.width
   # QUESTION is there a better way to do this?
   # I suppose we could have @tmp_files as an instance variable on converter instead
   # It might be sufficient to delete temporary files once per conversion
+  # NOTE Ruby 1.9 will sometimes delete a tmp file before the process exits
   def unlink_tmp_file path
-    path.unlink if TemporaryPath === path
+    path.unlink if TemporaryPath === path && path.exist?
   end
 
   # QUESTION move to prawn/extensions.rb?

lib/asciidoctor-pdf/temporary_path.rb

@@ -4,6 +4,10 @@ module TemporaryPath
   def unlink
     ::File.unlink self
   end
+
+  def exist?
+    ::File.file? self
+  end
 end
 end
 end