fix(zigbee_ep): fix variable scope

Co-authored-by: Copilot <[email protected]>

Author: SuGlider

Diff for: libraries/Zigbee/src/ZigbeeEP.cpp

@@ -263,7 +263,7 @@ void ZigbeeEP::zbReadBasicCluster(const esp_zb_zcl_attribute_t *attribute) {
   }
   if (attribute->id == ESP_ZB_ZCL_ATTR_BASIC_MODEL_IDENTIFIER_ID && attribute->data.type == ESP_ZB_ZCL_ATTR_TYPE_CHAR_STRING && attribute->data.value) {
     zbstring_t *zbstr = (zbstring_t *)attribute->data.value;
-    char *_read_model = (char *)malloc(zbstr->len + 1);
+    _read_model = (char *)malloc(zbstr->len + 1);
     if (_read_model == NULL) {
       log_e("Failed to allocate memory for model data");
       xSemaphoreGive(lock);