drm/amdgpu: Fix the null pointer dereference to ras_manager

Check ras_manager before using it
Signed-off-by: Ma Jun <Jun.Ma2@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c

@@ -2172,12 +2172,15 @@ static void amdgpu_ras_interrupt_process_handler(struct work_struct *work)
 int amdgpu_ras_interrupt_dispatch(struct amdgpu_device *adev,
 		struct ras_dispatch_if *info)
 {
-	struct ras_manager *obj = amdgpu_ras_find_obj(adev, &info->head);
-	struct ras_ih_data *data = &obj->ih_data;
+	struct ras_manager *obj;
+	struct ras_ih_data *data;
 
+	obj = amdgpu_ras_find_obj(adev, &info->head);
 	if (!obj)
 		return -EINVAL;
 
+	data = &obj->ih_data;
+
 	if (data->inuse == 0)
 		return 0;