Open this folder \Arduino\libraries\Blynk\src\Blynk then open the BlynkApi.h file then comment these lines

#if !defined(BLYNK_TEMPLATE_ID) || !defined(BLYNK_TEMPLATE_NAME)
 #error "Please specify your BLYNK_TEMPLATE_ID and BLYNK_TEMPLATE_NAME"
#endif

i hope this was helping