Operating system: Windows 10
Graphics card: Dell internal + Nvidia gtx 1050
Broken: 2.80, ff108aac631
Short description of error
Using the mirror modifier with a regular empty (plain axes) as the mirror object over x axis doesn't use the empty as the mirror plane. Also when pressing N in the dope sheet an empty window opens on the right.
Exact steps for others to reproduce the error
Create grease pencil object, add empty, use mirror modifier and set the empty as the mirror object, move empty and/or grease pencil object.