suggested fix for Bing Maps specific search error

for some reason, webmaps which uses Bing Maps basemap returns a null
spatialReference.  

using a webmapID like "ba4712dc554346aa9c5f7818cf99e93c" and attempting to search with the original code base shows the problem (the null spatialReference prohibits the query task from firing)

added a bit of a hacky approach to set the deferred map spatial reference to web mercator manually in this scenario, which solves the search problem.