* src/io/image_io.cc: Check the length of the input buffer.
* tests/python/unittest/test_image.py: Update the (already existing) test to expect a mx.base.MXNetError.

* src/io/image_io.cc: Raise an exception when the image could not be decoded instead of just logging.
* tests/python/unittest/test_image.py: Add a new test test_imdecode_invalid_image.

* src/io/image_io.cc: Raise an exception when the image could not be decoded instead of just logging.
* tests/python/unittest/test_image.py: Add a new test test_imdecode_invalid_image.

…ow more generally handled

in the core code.

* python/mxnet/image/image.py: remove buffer length check.

…into issue-11912