SRSUE: Avoid sf_worker return without calling worker_end

srsue/src/phy/sf_worker.cc

@@ -184,7 +184,7 @@ void sf_worker::work_imp()
 {
   std::lock_guard<std::mutex> lock(mutex);
   if (!cell_initiated) {
-    return;
+    phy->worker_end(this, false, nullptr, nullptr, tx_time);
   }
 
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