Map backend: continuous marker mode seems broken in standard deviation mode

[bobular]

All three variables I tried in the VectorBase map gave 500 errors like this. Pretty sure it used to be OK.

Likely an unintended consequence of binning-related tweaks a few months ago.

{"status":"server-error","message":"The variable value 234.0 is not in any specified bin range.","requestId":"4Ci279nagsAvl7LJdfBka7"}