parser: disallow the array init: attr, when the len: attr is not provided (#16735)

examples/graphs/bfs.v

@@ -16,7 +16,7 @@ fn main() {
 // Breadth-First Search (BFS) allows you to find the shortest distance between two nodes in the graph.
 fn breadth_first_search_path(graph map[string][]string, vertex string, target string) []string {
 	mut path := []string{}
-	mut visited := []string{init: vertex}
+	mut visited := []string{len: 6, init: vertex}
 	mut queue := [][][]string{}
 	queue << [[vertex], path]
 	for queue.len > 0 {