Use even more optional chaining in the src/display/api.js file

This slightly shortens the code, in various `destroy`-methods, which cannot hurt.
Also, use pre-processor checks to simplify `PDFDocumentLoadingTask.destroy` in the Firefox PDF Viewer since the `PDFWorker.fromPort`-method isn't used there.

src/display/api.js

@@ -655,23 +655,26 @@ class PDFDocumentLoadingTask {
    */
   async destroy() {
     this.destroyed = true;
-    try {
-      if (this._worker?.port) {
-        this._worker._pendingDestroy = true;
-      }
+
+    if (typeof PDFJSDev !== "undefined" && PDFJSDev.test("MOZCENTRAL")) {
       await this._transport?.destroy();
-    } catch (ex) {
-      if (this._worker?.port) {
-        delete this._worker._pendingDestroy;
+    } else {
+      try {
+        if (this._worker?.port) {
+          this._worker._pendingDestroy = true;
+        }
+        await this._transport?.destroy();
+      } catch (ex) {
+        if (this._worker?.port) {
+          delete this._worker._pendingDestroy;
+        }
+        throw ex;
       }
-      throw ex;
     }
-
     this._transport = null;
-    if (this._worker) {
-      this._worker.destroy();
-      this._worker = null;
-    }
+
+    this._worker?.destroy();
+    this._worker = null;
   }
 }
 
@@ -2336,17 +2339,16 @@ class PDFWorker {
    */
   destroy() {
     this.destroyed = true;
-    if (this._webWorker) {
-      // We need to terminate only web worker created resource.
-      this._webWorker.terminate();
-      this._webWorker = null;
-    }
+
+    // We need to terminate only web worker created resource.
+    this._webWorker?.terminate();
+    this._webWorker = null;
+
     PDFWorker.#workerPorts?.delete(this._port);
     this._port = null;
-    if (this._messageHandler) {
-      this._messageHandler.destroy();
-      this._messageHandler = null;
-    }
+
+    this._messageHandler?.destroy();
+    this._messageHandler = null;
   }
 
   /**
@@ -2600,10 +2602,9 @@ class WorkerTransport {
         new AbortException("Worker was terminated.")
       );
 
-      if (this.messageHandler) {
-        this.messageHandler.destroy();
-        this.messageHandler = null;
-      }
+      this.messageHandler?.destroy();
+      this.messageHandler = null;
+
       this.destroyCapability.resolve();
     }, this.destroyCapability.reject);
     return this.destroyCapability.promise;