fix: check the asset's existence before running filter
fix: check the asset's existence before running filter

fixes https://github.com/vuejs/vue-cli/issues/4572

EliteScientist/webpack,SimenB/webpack,NekR/webpack,SimenB/webpack,webpack/webpack,webpack/webpack,NekR/webpack,webpack/webpack,SimenB/webpack,SimenB/webpack,webpack/webpack,EliteScientist/webpack