Fix join with rel part of " ". Add a few tests.

test/nsurl.c

@@ -136,6 +136,12 @@ static const struct test_pairs join_tests[] = {
 	{ "http://",		"http:" },
 	{ "http:/",		"http:" },
 	{ "http:",		"http:" },
+	{ " ",			"http://a/b/c/d;p?q" },
+	{ "  ",			"http://a/b/c/d;p?q" },
+	{ "/",			"http://a/" },
+	{ "  /  ",		"http://a/" },
+	{ "  ?  ",		"http://a/b/c/d;p?" },
+	{ "  h  ",		"http://a/b/c/h" },
 	/* [1] Extra slash beyond rfc3986 5.4.1 example, since we're
 	 *     testing normalisation in addition to joining */
 	/* [2] Using the strict parsers option */

utils/nsurl.c

@@ -264,6 +264,13 @@ static void nsurl__get_string_markers(const char * const url_s,
 	marker.scheme_end = marker.authority = marker.colon_first = marker.at =
 			marker.colon_last = marker.path = marker.start;
 
+	if (*pos == '\0') {
+		/* Nothing but whitespace, early exit */
+		marker.query = marker.fragment = marker.end = marker.path;
+		*markers = marker;
+		return;
+	}
+
 	/* Get scheme */
 	if (isalpha(*pos)) {
 		pos++;