Recoverable error, Argument 2 to getChunk() must be of the type array, null given

[pixelchutes]

I've been seeing this recently on a few sites, and still trying to track down the root cause.

(ERROR @ core/model/modx/modx.class.php : 1812) Recoverable error: Argument 2 passed to modX::getChunk() must be of the type array, null given, called in core/components/login/model/login/login.class.php on line 221 and defined

Has anyone else experienced this yet, or know how the 2nd argument could be getting passed (as null)? I quickly looked at the code, but data type was not defined for $properties (2nd argument eventually passed to modx::getChunk).