Only add port if not already set

Author: geographika

docker/runtime/etc/apache2/conf-enabled/mapserver.conf

@@ -23,7 +23,8 @@ ScriptAliasMatch "^${MAPSERVER_BASE_PATH}" /usr/local/bin/mapserv_wrapper
   # Digital Ocean does not seem to pass this header back
   # even though HTTP_X_FORWARDED_HOST is
   # SetEnv HTTP_X_FORWARDED_PORT 443
-  RequestHeader set X-Forwarded-Port "443"
+  # Only set the header if it is not already present
+  RequestHeader set X-Forwarded-Port "443" env=!X_FORWARDED_PORT
 </LocationMatch>
 
 ExtendedStatus On