[C++] castDECIMAL_utf8 has undefined behaviour in case of invalid input value

Describe the bug, including details regarding any error messages, version, and platform.

When castDECIMAL_utf8 receives value that can not be parsed to number it returns without setting any values to 'out_high', 'out_low'.
For some complex expressions in projector this causes SIGSEGV due to llvm optimisations of IR code.

Component(s)

Gandiva