UPDATE by @unknown: Still affects cauldrons as of 0.17.0.2. (Also occurs with potions and water bottles.) Created a separate ticket for that problem: MCPE-19347.
It's like the reverse of MCPE-13798. (This is NOT a duplicate of that bug.) When picking up lava/water with an empty bucket in creative mode, you will be given a lava/water bucket in your inventory, which shouldn't happen. This is not happening on Win10 Edition 0.15.10, so I'm not sure if this is a Pocket-exclusive bug or new in the 0.16.0 beta versions. Tested this in an Android emulator, though I would assume that has nothing to do with this kind of bug.
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Partially fixed in 0.17.0.2. Still occurs when removing liquids from cauldrons... also just discovered it happens with potions/water bottles, too.
Moved the cauldron thing into a separate ticket: MCPE-19347. Marking this bug as fixed. (It was technically fixed in 0.17.0.2, even though the fix version is 1.0.0.)
This bug has been reported to our internal bug tracker for further testing and a fix. It is scheduled to be fixed in one of the future updates (no specific date can be provided).