UPSTREAM: ida: Fix crash in ida_free when the bitmap is empty

[ Upstream commit af73483f ]

The IDA usually detects double-frees, but that detection failed to
consider the case when there are no nearby IDs allocated and so we have a
NULL bitmap rather than simply having a clear bit.  Add some tests to the
test-suite to be sure we don't inadvertently reintroduce this problem.
Unfortunately they're quite noisy so include a message to disregard
the warnings.

Bug: 321878978
Reported-by: Zhenghan Wang <wzhmmmmm@gmail.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
(cherry picked from commit 5dbcdaf4dbfe074e9142991c5c28eef789c1f6c6)
Signed-off-by: Lee Jones <joneslee@google.com>
Change-Id: I4919e5c64af12f86fe1a91e1e9224a58eedbf345