docs: document that curl_url_cleanup(NULL) is a safe no-op

This has always been the case, but it was not documented.

The paragraph was copied verbatim from curl_easy_cleanup.3

Closes #11150

diff --git a/docs/libcurl/curl_url_cleanup.3 b/docs/libcurl/curl_url_cleanup.3
index f483d3a94ed3e975eed9a80a1438bb0210ba0a2c..2e32668e6dd7296152e5d0a574b1140da818a6df 100644 (file)
--- a/docs/libcurl/curl_url_cleanup.3
+++ b/docs/libcurl/curl_url_cleanup.3
@@ -32,6 +32,9 @@ void curl_url_cleanup(CURLU *handle);
 .fi
 .SH DESCRIPTION
 Frees all the resources associated with the given \fICURLU\fP handle!
+
+Passing in a NULL pointer in \fIhandle\fP will make this function return
+immediately with no action.
 .SH EXAMPLE
 .nf
   CURLU *url = curl_url();