Error message showing up in log

I have a rule to hide the billing pane when order total is 0. The rule works as it should, but I also get this message in my log:

"Unable to get the data value for the variable or parameter data. Error: Unable to get the data property amount as the parent data structure is not set."

Here's the rule:
{ "rules_hide_billing_pane_if_not_needed" : {
"LABEL" : "Hide Billing Pane If Not Needed",
"PLUGIN" : "reaction rule",
"REQUIRES" : [ "rules", "commerce_rules_extra" ],
"ON" : [ "process_checkout_pane" ],
"IF" : [
{ "data_is" : {
"data" : [ "site:current-cart-order:commerce-order-total:amount" ],
"op" : "\u003C",
"value" : "0"
}
}
],
"DO" : [
{ "commerce_rules_extra_change_pane" : {
"pane_id" : "customer_profile_billing",
"page_id" : "\u003Csame\u003E",
"enabled" : 0
}
}
]
}
}