fix typo

lib/print.c

@@ -289,7 +289,7 @@ static size_t vsnprintf(char** str, size_t* size, const char *format, va_list va
 	}
 end:
 	if (NULL!=str && NULL!=*str && NULL!=size) { // when working on a string
-		*str='\0'; // enforce null termination
+		**str='\0'; // enforce null termination
 	}
 	return length; // return number of characters it should have written
 }