Add nullptr check for String TLV data with zero length

src/data-model-providers/codegen/EmberAttributeDataBuffer.cpp

@@ -244,6 +244,7 @@ CHIP_ERROR EmberAttributeDataBuffer::DecodeAsString(chip::TLV::TLVReader & reade
     // data copy
     const uint8_t * tlvData;
     ReturnErrorOnFailure(reader.GetDataPtr(tlvData));
+    VerifyOrReturnError(tlvData != nullptr, CHIP_ERROR_INVALID_TLV_ELEMENT);
     writer.Put(tlvData, stringLength);
 
     return CHIP_NO_ERROR;