Fix the missing default bbox_mode in the show_multi_modality_result (#825)

mmdet3d/core/visualizer/show_result.py

@@ -203,7 +203,7 @@ def show_multi_modality_result(img,
                                proj_mat,
                                out_dir,
                                filename,
-                               box_mode,
+                               box_mode='lidar',
                                img_metas=None,
                                show=True,
                                gt_bbox_color=(61, 102, 255),
@@ -220,8 +220,8 @@ def show_multi_modality_result(img,
             according to the camera intrinsic parameters.
         out_dir (str): Path of output directory.
         filename (str): Filename of the current frame.
-        box_mode (str): Coordinate system the boxes are in.
-            Should be one of 'depth', 'lidar' and 'camera'.
+        box_mode (str): Coordinate system the boxes are in. Should be one of
+           'depth', 'lidar' and 'camera'. Defaults to 'lidar'.
         img_metas (dict): Used in projecting depth bbox.
         show (bool): Visualize the results online. Defaults to False.
         gt_bbox_color (str or tuple(int)): Color of bbox lines.