fix postinstall (#4359)

Author: elalish

scripts/postinstall.js

@@ -3,7 +3,8 @@ const THREE_REGEX = /three@[~^]?([\dvx*]+(?:[-.](?:[\dx*]+|alpha|beta))*)/gm;
 let NEW_THREE_VERSION;
 const THREE_PACKAGE_REGEX = /"three": ".*"/g;
 fs.readFile('package.json', {encoding: 'utf8'}, (err, data) => {
-  NEW_THREE_VERSION = `three@${THREE_PACKAGE_REGEX.exec(data)[0].split(' ')[1].replaceAll('"', '')}`;
+  NEW_THREE_VERSION = `three@${
+      THREE_PACKAGE_REGEX.exec(data)[0].split(' ')[1].replaceAll('"', '')}`;
   console.log(NEW_THREE_VERSION);
 });
 
@@ -14,9 +15,15 @@ function updateThreeVersion(filePath) {
       return;
     }
     const OLD_THREE_VERSION = THREE_REGEX.exec(data)[0];
+    if (!OLD_THREE_VERSION || !NEW_THREE_VERSION) {
+      console.error(
+          'Tried to replace ', OLD_THREE_VERSION, ' with ', NEW_THREE_VERSION);
+      return;
+    }
     data = data.replaceAll(OLD_THREE_VERSION, NEW_THREE_VERSION);
     fs.writeFile(filePath, data, {encoding: 'utf8'}, (err) => {
-      if (err) console.log(err);
+      if (err)
+        console.log(err);
     });
   });
 }