Error when updating Pending Contribution
I believe this is the same underlying error reported here:
https://issues.civicrm.org/jira/browse/CRM-20297

Specifically, contributions containing line items without a matching priceset can cause problems (because CiviCRM tries to match them up with priceset items and can generate errors when it does that badly).

It seems likely this error can be fixed using the patch provided for that issue, here:

https://github.com/civicrm/civicrm-core/pull/10012

Here's a short cut url to to a patch ready version of that pull request:

https://github.com/civicrm/civicrm-core/pull/10012.diff