On AMD, don't release kernel args if they haven't been allocated

Author: RossBrunton

offload/plugins-nextgen/amdgpu/src/rtl.cpp

@@ -1261,9 +1261,11 @@ struct AMDGPUStreamTy {
     // Consume stream slot and compute dependencies.
     auto [Curr, InputSignal] = consume(OutputSignal);
 
-    // Setup the post action to release the kernel args buffer.
-    if (auto Err = Slots[Curr].schedReleaseBuffer(KernelArgs, MemoryManager))
-      return Err;
+    // Setup the post action to release the kernel args buffer, if it exists
+    if (KernelArgs) {
+      if (auto Err = Slots[Curr].schedReleaseBuffer(KernelArgs, MemoryManager))
+        return Err;
+    }
 
     // If we are running an RPC server we want to wake up the server thread
     // whenever there is a kernel running and let it sleep otherwise.