bus-message: fix calculation of offsets table

The offsets specify the ends of variable length data. We would trust the
incoming data, putting the offsets specified in our message
into the offsets tables after doing some superficial verification.
But when actually reading the data we apply alignment, so we would take
the previous offset, align it, making it bigger then current offset, and
then we'd try to read data of negative length.

In the attached example, the message specifies the following offsets:
[1, 4]
but the alignment of those items is
[1, 8]
so we'd calculate the second item as starting at 8 and ending at 4.

1 files changed, 0 insertions, 0 deletions

diff --git a/test/fuzz/fuzz-bus-message/crash-e1b811da5ca494e494b77c6bd8e1c2f2989425c5 b/test/fuzz/fuzz-bus-message/crash-e1b811da5ca494e494b77c6bd8e1c2f2989425c5
new file mode 100644
index 0000000000..9d3fa0035f
--- /dev/null
+++ b/test/fuzz/fuzz-bus-message/crash-e1b811da5ca494e494b77c6bd8e1c2f2989425c5