!164 支持element目录下string资源配置为空字符串

Merge pull request !164 from liduo/string_can_be_empty

src/resource_item.cpp

@@ -47,11 +47,17 @@ bool ResourceItem::SetData(const string &data)
 
 bool ResourceItem::SetData(const int8_t *data, uint32_t length)
 {
-    if (data == nullptr || length <= 0) {
+    if (data == nullptr || length < 0) {
         return false;
     }
 
     ReleaseData();
+    if (length == 0) {
+        // the string in the element directory can be empty
+        data_ = new (nothrow) int8_t[0];
+        dataLen_ = 0;
+        return true;
+    }
     int8_t *buffer = reinterpret_cast<int8_t *>(new (nothrow) int8_t[length]);
     if (buffer == nullptr) {
         return false;