Fix isCustomSearchPrimarySuggestion
Fix isCustomSearchPrimarySuggestion

During the migration of this from coffeescript to javascript, some small
changes were introduced:
Before: https://github.com/philc/vimium/blob/478cc8ba4f0aa608b5cd044304221bc11932dd8b/pages/vomnibar.coffee#L162
After:  https://github.com/philc/vimium/commit/478cc8ba4f0aa608b5cd044304221bc11932dd8b#diff-f82dc63d5c5f05dc11ebc40b4e780fc11e3b65609b584fbb194f58bdd272e1c9R205-R206

1. the undefined value `c.isCustomSearchPrimarySuggestion` is read, instead of `c.isPrimarySuggestion`
2. `this.lastResponse` is used, instead of `this.lastReponse` (which is misspelled everywhere ese)

This commit reverts to the old version and fixes the behavior as
described in the 'second case' of the comment below.

philc/vimium,smblott-github/vimium,gdh1995/vimium,smblott-github/vimium,gdh1995/vimium,philc/vimium,smblott-github/vimium,philc/vimium,gdh1995/vimium