fix out-of-bounds read in isBlackboardPointer whitespace trim

[aysha-afrah26]

isBlackboardPointer trims leading and trailing spaces with two while loops before it checks for the {...} pattern, and each loop tests the character before it tests the index against the bounds. Because of the short-circuit order, str[front_index] is read first and front_index <= last_index only after. When the whole value is spaces, front_index walks up to str.size() and the loop reads one element past the end before the bounds check would have stopped it. The argument is a std::string_view, so that trailing byte is not guaranteed to be there; I ran into it under AddressSanitizer, which reports a heap-buffer-overflow read on a non null-terminated view of three spaces. Swapping the two operands so the bounds check runs first closes the read and leaves the trimming behavior unchanged. I added a regression test in gtest_ports that fails under ASan before the change and passes after.