vweb: fix route matching on `/` (#10001)

vlib/vweb/route_test.v

@@ -55,6 +55,10 @@ fn test_route_no_match() {
 			url: '/a/b/c/d'
 			route: '/a/b/c'
 		},
+		RoutePair{
+			url: '/a/b/c'
+			route: '/'
+		},
 	]
 	for test in tests {
 		test.test_no_match()

vlib/vweb/vweb.v

@@ -443,7 +443,7 @@ fn route_matches(url_words []string, route_words []string) ?[]string {
 	}
 
 	// The last route can end with ... indicating an array
-	if !route_words[route_words.len - 1].ends_with('...') {
+	if route_words.len == 0 || !route_words[route_words.len - 1].ends_with('...') {
 		return none
 	}