Update RawEmail patch

In development occasionally see errors where the original data isn't
present, normally when my local ActiveStorage store has been cleared.

We can return nil here and some dev operations (EG. indexing) will then
succeed.

lib/model_patches.rb

@@ -128,7 +128,7 @@ def is_school?
     alias original_data data
 
     def data
-      original_data.sub(/
+      original_data&.sub(/
         ^(Date: [^\n]+\n)
         \s+(To: [^\n]+\n)
         \s+(From: [^\n]+)