fix(zigbee_ep): replace nullptr by NULL after C malloc()

Author: SuGlider

libraries/Zigbee/src/ZigbeeEP.cpp

@@ -251,7 +251,7 @@ void ZigbeeEP::zbReadBasicCluster(const esp_zb_zcl_attribute_t *attribute) {
   if (attribute->id == ESP_ZB_ZCL_ATTR_BASIC_MANUFACTURER_NAME_ID && attribute->data.type == ESP_ZB_ZCL_ATTR_TYPE_CHAR_STRING && attribute->data.value) {
     zbstring_t *zbstr = (zbstring_t *)attribute->data.value;
     char *_read_manufacturer = (char *) malloc(zbstr->len + 1);
-    if (_read_manufacturer == nullptr) {
+    if (_read_manufacturer == NULL) {
       log_e("Failed to allocate memory for manufacturer data");
       xSemaphoreGive(lock);
       return;
@@ -264,7 +264,7 @@ 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);
-    if (_read_model == nullptr) {
+    if (_read_model == NULL) {
       log_e("Failed to allocate memory for model data");
       xSemaphoreGive(lock);
       return;