修复datepicker datetimepicker空值问题

vendor/blobt/widgets/DatePicker.php

@@ -133,7 +133,9 @@ SCRIPT;
 
         if ($this->hasModel()) {
             $timestamp = ArrayHelper::getValue($this->model, $this->attribute);
-            $value = date($this->format, $timestamp);
+            if (!empty($timestamp)) {
+                $value = date($this->format, $timestamp);
+            }
         }
 
         if (empty($timestamp) && $this->autoFill) {

vendor/blobt/widgets/DatetimePicker.php

@@ -133,7 +133,9 @@ SCRIPT;
 
         if ($this->hasModel()) {
             $timestamp = ArrayHelper::getValue($this->model, $this->attribute);
-            $value = date($this->format, $timestamp);
+            if (!empty($timestamp)) {
+                $value = date($this->format, $timestamp);
+            }
         }
 
         if (empty($timestamp) && $this->autoFill) {