Remove backslash from image search host

boards/models/attachment/viewers.py

@@ -81,6 +81,8 b' class AbstractViewer:'
     def get_view(self):
         search_host = settings.get('External', 'ImageSearchHost')
         if search_host:
+            if search_host.endswith('/'):
+                search_host = search_host[:-1]
             search_url = search_host + self.file.url
         else:
             search_url = ''