Currently, the _read_bson_doc() function in dsi/libanalysis/readers.py throws when it encounters the valid BSON element type of 0xa, or the "null" type.

After PM-3290, the output of getParameter will be appearing in FTDC files as "periodic metadata" type (type 2) records. This means that "null" type BSON elements may now appear in FTDC (for instance, if unset, the clusterIpSourceAllowlist server parameter serializes to a "null" type in the getParameter output)