comment why we do body = '' when there is not response body

Author: Glynn Bird

lib/nano.js

@@ -197,6 +197,11 @@ module.exports = exports = function dbScope (cfg) {
     try {
       body = await response.json()
     } catch (e) {
+      // if we were expecting a JSON response but didn't get one, set the body to a blank string
+      // rather than throw an error. This happens when 
+      // - we do HEAD /db/docid
+      // - or we get a 500 from CouchDB with no body
+      // In these cases we expect a rejected promise.
       body = ''
     }