allow multiple subscribers on same node

just/observable-test.fnl

@@ -57,3 +57,11 @@
   (s:observe [:foo :bar] #(set win 4))
   (s:update [:foo :bar :baz] 42)
   (expect (= win 2)))
+
+(let [s (observable.new {:foo {:bar {:baz 43}}})]
+  (var win 0)
+  ;; multiple observers can live on same subtree
+  (s:observe [:foo :bar] #(set win (+ win 1)))
+  (s:observe [:foo :bar] #(set win (+ win 1)))
+  (s:update [:foo :bar :baz] 42)
+  (expect (= win 2)))

just/observable.fnl

@@ -21,7 +21,7 @@
   (let [el (get data self path)]
     (when el
       (if el._subscribers
-          (el._subscribers:insert fun)
+          (table.insert el._subscribers fun)
           (tset el :_subscribers [fun])))))
 
 (fn new [data]