Use more optional chaining in the code-base (PR 15398 follow-up)

*Fixes a few cases that I missed in PR 15398.*

src/display/fetch_stream.js

@@ -190,12 +190,11 @@ class PDFFetchStreamReader {
       return { value, done };
     }
     this._loaded += value.byteLength;
-    if (this.onProgress) {
-      this.onProgress({
-        loaded: this._loaded,
-        total: this._contentLength,
-      });
-    }
+    this.onProgress?.({
+      loaded: this._loaded,
+      total: this._contentLength,
+    });
+
     const buffer = new Uint8Array(value).buffer;
     return { value: buffer, done: false };
   }

src/display/node_stream.js

@@ -163,12 +163,11 @@ class BaseFullReader {
       return this.read();
     }
     this._loaded += chunk.length;
-    if (this.onProgress) {
-      this.onProgress({
-        loaded: this._loaded,
-        total: this._contentLength,
-      });
-    }
+    this.onProgress?.({
+      loaded: this._loaded,
+      total: this._contentLength,
+    });
+
     // Ensure that `read()` method returns ArrayBuffer.
     const buffer = new Uint8Array(chunk).buffer;
     return { value: buffer, done: false };

src/display/transport_stream.js

@@ -92,15 +92,12 @@ class PDFDataTransportStream {
   _onProgress(evt) {
     if (evt.total === undefined) {
       // Reporting to first range reader, if it exists.
-      const firstReader = this._rangeReaders[0];
-      if (firstReader?.onProgress) {
-        firstReader.onProgress({ loaded: evt.loaded });
-      }
+      this._rangeReaders[0]?.onProgress?.({ loaded: evt.loaded });
     } else {
-      const fullReader = this._fullRequestReader;
-      if (fullReader?.onProgress) {
-        fullReader.onProgress({ loaded: evt.loaded, total: evt.total });
-      }
+      this._fullRequestReader?.onProgress?.({
+        loaded: evt.loaded,
+        total: evt.total,
+      });
     }
   }