Improve check_imshow() robustness (#4483)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

tests/test_python.py

@@ -311,14 +311,15 @@ def test_utils_init():
 
 
 def test_utils_checks():
-    from ultralytics.utils.checks import (check_imgsz, check_requirements, check_yolov5u_filename, git_describe,
-                                          print_args)
+    from ultralytics.utils.checks import (check_imgsz, check_imshow, check_requirements, check_yolov5u_filename,
+                                          git_describe, print_args)
 
     check_yolov5u_filename('yolov5n.pt')
     # check_imshow(warn=True)
     git_describe(ROOT)
     check_requirements()  # check requirements.txt
     check_imgsz([600, 600], max_dim=1)
+    check_imshow()
     print_args()