fix $boolean for functions

Author: zirkelc

src/functions.js

@@ -1420,7 +1420,7 @@ const functions = (() => {
             if (arg !== 0) {
                 result = true;
             }
-        } else if (arg !== null && typeof arg === 'object') {
+        } else if (arg !== null && typeof arg === 'object' && !isFunction(arg)) {
             if (Object.keys(arg).length > 0) {
                 result = true;
             }