Ensure getFuncName returns a string.

lodash.src.js

@@ -4009,7 +4009,7 @@
      * @returns {string} Returns the function name.
      */
     function getFuncName(func) {
-      var result = func.name,
+      var result = (func.name + ''),
           array = realNames[result],
           length = array ? array.length : 0;
 
@@ -12487,7 +12487,7 @@
     baseForOwn(LazyWrapper.prototype, function(func, methodName) {
       var lodashFunc = lodash[methodName];
       if (lodashFunc) {
-        var key = lodashFunc.name,
+        var key = (lodashFunc.name + ''),
             names = realNames[key] || (realNames[key] = []);
 
         names.push({ 'name': methodName, 'func': lodashFunc });