An invisible entity that makes no sound and emites potion effect bubbles spawned in my survival mode minecraft world. When I killed it, it showed the death smoke but dropped nothing.

Wandering Trader or invisible Witch?

Could also be a invisible spider

Thank you for your report!
However, this issue is Incomplete.

Your report does not contain enough information. As such, we're unable to understand or reproduce the problem.
Please review the guidelines linked below before making further reports.

In case of a game crash, be sure to attach the crashlog from [minecraft/crash-reports/crash-<DATE>-client.txt|http://hopper.minecraft.net/help/guides/finding-minecraft-data-folder].

Quick Links:
📓 Issue Guidelines – 💬 Community Support – 📧 Customer Support – 📖 Game Wiki