Fix bug when setting the minimum date but not defining the model

bower.json

@@ -1,6 +1,6 @@
 {
   "name": "ngComboDatePicker",
-  "version": "1.5.0",
+  "version": "1.5.1",
   "authors": [
     "jfmdev <jfmdev@outlook.com>"
   ],

package.json

@@ -1,6 +1,6 @@
 {
   "name": "ng-combo-date-picker",
-  "version": "1.5.0",
+  "version": "1.5.1",
   "description": "An Angular directive to select dates using combo boxes",
   "main": "source/ngComboDatePicker.js",
   "scripts": {

source/ngComboDatePicker.js

@@ -1,5 +1,5 @@
 /*
- * ngComboDatePicker v1.5.0
+ * ngComboDatePicker v1.5.1
  * http://github.com/jfmdev/ngComboDatePicker
  * «Copyright 2015 Jose F. Maldonado»
  * This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0. If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
@@ -145,8 +145,8 @@ angular.module("ngComboDatePicker", [])
                 }
 
                 // Verify if selected date is in the valid range.
-                if($scope.ngMinModel &&$scope.ngModel < $scope.ngMinModel) $scope.ngModel = $scope.ngMinModel;
-                if($scope.ngMaxModel && $scope.ngModel > $scope.ngMaxModel) $scope.ngModel = $scope.ngMaxModel;
+                if($scope.ngModel && $scope.ngMinModel && $scope.ngModel < $scope.ngMinModel) $scope.ngModel = $scope.ngMinModel;
+                if($scope.ngModel && $scope.ngMaxModel && $scope.ngModel > $scope.ngMaxModel) $scope.ngModel = $scope.ngMaxModel;
             });
 
             // Initialize place holders.