*Change pullRemote to throw if the item is not empty

index.js

@@ -777,12 +777,15 @@ module.exports = class Protomux {
   async popFree(id) {
     await this.userData.syncProtomux("popFree", id);
   }
+
   async pushFree(id) {
     await this.userData.syncProtomux("pushFree", id);
   }
+
   async pushLocal(id) {
     await this.userData.syncProtomux("pushLocal", id);
   }
+
   async pushRemote(id) {
     await this.userData.syncProtomux("pushRemote", id);
   }
@@ -797,20 +800,23 @@ module.exports = class Protomux {
       }
     });
   }
+
   async pullFree() {
     const ids = await this.userData.syncProtomux("pullFree");
 
     this._free = Array.from(new Set([...this._free, ...ids]));
     this._free = this._free.filter((item) => item !== null);
   }
+
   async pullRemote() {
     const ids = await this.userData.syncProtomux("pullRemote");
 
     ids.forEach((item) => {
       item = parseInt(item);
-      if (typeof this._remote[item] === "undefined") {
-        this._remote[item] = null;
+      if (typeof this._remote[item] !== "undefined") {
+        throw new Error("empty remote element expected");
       }
+      this._remote[item] = null;
     });
   }
 };