fix getBackup panic if pass a invalid backup ID (#424)

Signed-off-by: wayblink <[email protected]>

Author: wayblink

core/backup_context.go

@@ -647,13 +647,13 @@ func (b *BackupContext) GetRestore(ctx context.Context, request *backuppb.GetRes
 	}
 
 	task := b.meta.GetRestoreTask(request.GetId())
-	progress := int32(float32(task.GetRestoredSize()) * 100 / float32(task.GetToRestoreSize()))
-	// don't return zero
-	if progress == 0 {
-		progress = 1
-	}
-	task.Progress = progress
 	if task != nil {
+		progress := int32(float32(task.GetRestoredSize()) * 100 / float32(task.GetToRestoreSize()))
+		// don't return zero
+		if progress == 0 {
+			progress = 1
+		}
+		task.Progress = progress
 		resp.Code = backuppb.ResponseCode_Success
 		resp.Msg = "success"
 		resp.Data = task