insights: Don't return an error when checking for default mode on a standard query

Created by: CristinaBirkel

Description

When getting a default aggregation mode, canAggregateByCaptureGroup is calling NewPatternReplacer to check to see if there are any capture groups. NewPatternReplacer returns errors if it isn't a regexp, and we don't want to throw an error on that if we're just using it to check for capture groups.

So the solution here is to check specifically for that error, and to return false instead of an error when it's hit.

Test plan

First, run a standard query that will check for the default mode. Example:

{
  searchQueryAggregate(query: "graphql.NewSchema", patternType: standard) {
    aggregations(limit: 10) {
      __typename
      ... on ExhaustiveSearchAggregationResult {
        groups {
          label
          count
          query
        }
        otherResultCount
        otherGroupCount
      }
      ... on SearchAggregationNotAvailable {
        reason
      }
    }
  }
}

Verify that you get a "pattern parsing" error. Then try again with this fix in place and verify that it works.