SWDEV-497841 - Avoid access to the null stream on mempool alloc

Null stream isn't created during the device creation

hipamd/src/hip_mempool_impl.hpp

@@ -214,7 +214,7 @@ class MemoryPool : public amd::ReferenceCountedObject, amd::VmHeap {
   };
 
   MemoryPool(hip::Device* device, const hipMemPoolProps* props = nullptr, bool phys_mem = false)
-      : VmHeap(device->asContext()->devices()[0], *device->NullStream()),
+      : VmHeap(device->devices()[0]),
         busy_heap_(device, *this),
         free_heap_(device, *this),
         lock_pool_ops_(true),
@@ -259,6 +259,9 @@ class MemoryPool : public amd::ReferenceCountedObject, amd::VmHeap {
     }
   }
 
+  /// Returns a queue for virtual memory map/unmap operations
+  virtual amd::HostQueue& GetVmQueue() final { return *device_->NullStream(); }
+
   /// The same stream can reuse memory without HIP event validation
   void* AllocateMemory(size_t size, Stream* stream, void* dptr = nullptr);