Ensure _.keysIn treats primitives like objects and both _.keys and _.keysIn return empty arrays for null and undefined values.

lodash.js

@@ -6984,6 +6984,8 @@
       if (object == null) {
         return [];
       }
+      object = Object(object);
+
       var length = object.length;
       length = (typeof length == 'number' && length > 0 &&
         (isArray(object) || (support.nonEnumStrings && isString(object)) ||