When handling inlined landing / eh pad, we may split a block. But we didn't copy BFI to the new block.
This leads to non-deterministic behavior.
In some cases, BlockFrequencyInfoImplBase::getBlockFreq can detect this unknown block and return 0.
In other rare cases, the BasicBlock* happens to be an address used before, an old frequency value will be returned.
This error can be easily detected if -check-bfi-unknown-block-queries is enabled.