endpoint: Allow to pass NULL params in no query string case

Previously if you had an endpoint that only took an optional query
string and didn't want to pass one then you had to construct a params
array with a NULL member.

Make it so that in this case you can also just pass NULL, as you can do
for an endpoint that does not take any parameters.

Signed-off-by: Andrew Clayton <ac@sigsegv.uk>

Author: ac000

docs/man/man3/mtd_ep.3

@@ -1,6 +1,6 @@
 .\" Automatically generated by Pandoc 3.7.0.2
 .\"
-.TH "mtd_ep" "3" "May 19, 2026" "Version 1.6.2" "libmtdac"
+.TH "mtd_ep" "3" "May 23, 2026" "Version 1.6.2+" "libmtdac"
 .SH NAME
 \f[B]mtd_ep\f[R] \- send query to API endpoint
 .SH LIBRARY
@@ -58,11 +58,9 @@ extras will be ignored.
 There is no need to pass in how many entries is in params (or for it to
 be NULL terminated) as this is dictated by each endpoint.
 .PP
-For any endpoints which don\(cqt require \f[I]any\f[R] parameters, this
-can be \f[B]NULL\f[R].
-If an endpoint \f[I]only\f[R] takes an \f[I]optional\f[R] query stirng,
-then you still need a params with a single entry either containing NULL
-or a valid query string.
+For any endpoints which don\(cqt require \f[I]any\f[R] parameters,
+including endpoints that take an optional query string where you
+don\(aqt want to pass one, this can be \f[B]NULL\f[R].
 .PP
 \f[B]NOTE:\f[R] nino (National Insurance Number) is not included in the
 above as that is acquired by libmtdac via other means.

docs/mtd_ep.3.rst

@@ -57,10 +57,9 @@ This function is used to send a query to a specified API endpoint.
    There is no need to pass in how many entries is in params (or for it
    to be NULL terminated) as this is dictated by each endpoint.
 
-   For any endpoints which don’t require *any* parameters, this can be
-   **NULL**. If an endpoint *only* takes an *optional* query stirng,
-   then you still need a params with a single entry either containing
-   NULL or a valid query string.
+   For any endpoints which don’t require *any* parameters, including
+   endpoints that take an optional query string where you don't want to
+   pass one, this can be **NULL**.
 
    **NOTE:** nino (National Insurance Number) is not included in the
    above as that is acquired by libmtdac via other means.

src/endpoint.c

@@ -164,7 +164,7 @@ char *ep_make_url(enum mtd_api_endpoint ep, const char * const params[],
 			snprintf(url + len, URL_LEN+1 - len, "/%s", nino);
 		else if (strstr(token, "query_params"))
 			snprintf(url + len, URL_LEN+1 - len, "%s",
-				 params[p] ? params[p++] : "");
+				 params && params[p] ? params[p++] : "");
 		else
 			snprintf(url + len, URL_LEN+1 - len, "/%s",
 				 params[p++]);