add strict null check and fix codes

src/index.ts

@@ -1,4 +1,5 @@
 import snapshot from './snapshot';
 import rebuild from './rebuild';
+export * from './types';
 
 export { snapshot, rebuild };

src/rebuild.ts

@@ -62,7 +62,11 @@ function rebuild(n: serializedNodeWithId): Node | null {
   if (n.type === NodeType.Document || n.type === NodeType.Element) {
     for (const childN of n.childNodes) {
       const childNode = rebuild(childN);
-      root.appendChild(childNode);
+      if (!childNode) {
+        console.warn('Failed to rebuild', childN);
+      } else {
+        root.appendChild(childNode);
+      }
     }
   }
   return root;

src/snapshot.ts

@@ -98,7 +98,7 @@ function serializeNode(n: Node, doc: Document): serializedNode | false {
       }
       return {
         type: NodeType.Text,
-        textContent,
+        textContent: textContent || '',
       };
     case n.CDATA_SECTION_NODE:
       return {
@@ -108,7 +108,7 @@ function serializeNode(n: Node, doc: Document): serializedNode | false {
     case n.COMMENT_NODE:
       return {
         type: NodeType.Comment,
-        textContent: (n as Comment).textContent,
+        textContent: (n as Comment).textContent || '',
       };
     default:
       return false;
@@ -130,7 +130,10 @@ function _snapshot(n: Node, doc: Document): serializedNodeWithId | null {
     serializedNode.type === NodeType.Element
   ) {
     for (const childN of Array.from(n.childNodes)) {
-      serializedNode.childNodes.push(_snapshot(childN, doc));
+      const serializedChildNode = _snapshot(childN, doc);
+      if (serializedChildNode) {
+        serializedNode.childNodes.push(serializedChildNode);
+      }
     }
   }
   return serializedNode;