Added checks to ensure that the configs are valid before starting eval

Editor assessment

The subject states the safeguard plainly: checks ensure configs are valid before evaluation starts, with the issue reference conventionally attached. The timing and the guard are both clear without the diff. The fix type fits a defensive correction. No body explains what invalid configs caused previously — presumably crashes or silent misbehavior — which is the rationale a body would carry, but the essential behavior is communicated and the change is contained. Style is clean apart from the past-tense verb. Good and publishable.