Extract a worker var in allocateUnusedWorker. NFC (#18304)

Author: RReverser

src/library_pthread.js

@@ -404,6 +404,7 @@ var LibraryPThread = {
 
     // Creates a new web Worker and places it in the unused worker pool to wait for its use.
     allocateUnusedWorker: function() {
+      var worker;
 #if MINIMAL_RUNTIME
       var pthreadMainJs = Module['worker'];
 #else
@@ -424,12 +425,11 @@ var LibraryPThread = {
               }
             }
           );
-          PThread.unusedWorkers.push(new Worker(p.createScriptURL('ignored')));
+          worker = new Worker(p.createScriptURL('ignored'));
         } else
 #endif
-        PThread.unusedWorkers.push(new Worker(new URL('{{{ PTHREAD_WORKER_FILE }}}', import.meta.url)));
-        return;
-      }
+        worker = new Worker(new URL('{{{ PTHREAD_WORKER_FILE }}}', import.meta.url));
+      } else {
 #endif
       // Allow HTML module to configure the location where the 'worker.js' file will be loaded from,
       // via Module.locateFile() function. If not specified, then the default URL 'worker.js' relative
@@ -443,10 +443,14 @@ var LibraryPThread = {
       // Use Trusted Types compatible wrappers.
       if (typeof trustedTypes != 'undefined' && trustedTypes.createPolicy) {
         var p = trustedTypes.createPolicy('emscripten#workerPolicy2', { createScriptURL: function(ignored) { return pthreadMainJs } });
-        PThread.unusedWorkers.push(new Worker(p.createScriptURL('ignored')));
+        worker = new Worker(p.createScriptURL('ignored'));
       } else
 #endif
-      PThread.unusedWorkers.push(new Worker(pthreadMainJs));
+      worker = new Worker(pthreadMainJs);
+#if EXPORT_ES6 && USE_ES6_IMPORT_META
+    }
+#endif
+    PThread.unusedWorkers.push(worker);
     },
 
     getNewWorker: function() {