fix(repeat): null/undefined should not cause error
fix(repeat): null/undefined should not cause error

Fixes #35

martingust/templating-resources,aurelia/templating-resources,cmichaelgraham/templating-resources,jdanyow/templating-resources,aurelia/templating-resources,aurelia/templating-resources,marknutter/templating-resources,hitesh97/templating-resources