fix replace with delete

src/structs/AbstractItem.js

@@ -421,6 +421,13 @@ export class AbstractItem extends AbstractStruct {
       if (r.right !== null) {
         r.right.left = r
       }
+      if (r.left === null) {
+        if (r.parentSub === null) {
+          r.parent._start = r
+        } else {
+          r.parent._map.set(r.parentSub, r)
+        }
+      }
     }
     replaceStruct(y.store, this, r)
     return r

src/utils/Y.js

@@ -12,7 +12,8 @@ import {
   YText,
   YMap,
   YXmlFragment,
-  YEvent, ItemDeleted, GC, AbstractStruct // eslint-disable-line
+  ItemDeleted,
+  YEvent, GC, AbstractStruct // eslint-disable-line
 } from '../internals.js'
 
 import { Observable } from 'lib0/observable.js'
@@ -121,7 +122,7 @@ export class Y extends Observable {
                 if (deleteItem.clock + deleteItem.len < struct.id.clock) {
                   break
                 }
-                if (struct.deleted && struct instanceof AbstractItem) {
+                if (struct.deleted && struct instanceof AbstractItem && (struct.constructor !== ItemDeleted || (struct.parent._item !== null && struct.parent._item.deleted))) {
                   // check if we can GC
                   replacedItems.add(struct.gc(this))
                 }