fix: unknown "trust_forwarded_proto" variable error when run with already created old virtual hosts

docker/rootfs/etc/nginx/conf.d/include/force-ssl.conf

@@ -8,7 +8,10 @@ if ($request_uri = /.well-known/acme-challenge/test-challenge) {
 
 # Check if the ssl staff has been handled
 set $test_ssl_handled "";
-if ($trust_forwarded_proto = T){
+if ($trust_forwarded_proto = "") {
+	set $trust_forwarded_proto "F";
+}
+if ($trust_forwarded_proto = "T") {
 	set $test_ssl_handled "${test_ssl_handled}T";
 }
 if ($http_x_forwarded_proto = "https") {