Fix errors resulting from #318

When commit ddfc3a8300 ("Run file_data_filter on deleted files")
started calling the file_data_filter plugin method, in order to make
deletion of plugin-renamed files work, the example plugins were not
updated. This commit updates the example plugins to not crash when the
file context is None.

Thanks to @hetas discovering this.

Closes 328

plugins/dos2unix/__init__.py

@@ -6,6 +6,8 @@ class Filter():
         pass
 
     def file_data_filter(self,file_data):
+        if file_data['file_ctx'] == None:
+            return
         file_ctx = file_data['file_ctx']
         if not file_ctx.isbinary():
             file_data['data'] = file_data['data'].replace(b'\r\n', b'\n')

plugins/shell_filter_file_contents/__init__.py

@@ -15,6 +15,8 @@ class Filter:
         d = file_data['data']
         file_ctx = file_data['file_ctx']
         filename = file_data['filename']
+        if file_ctx == None:
+            return
         filter_cmd = self.filter_contents + [filename, node.hex(file_ctx.filenode()), '1' if file_ctx.isbinary() else '0']
         try:
             filter_proc = subprocess.Popen(filter_cmd, stdin=subprocess.PIPE, stdout=subprocess.PIPE)