Your device is rooted , so you could try Gravity Box Xposed module has to disable pattern error - thanks to Cool Guy's comment
That aside, since you are security minded
Pattern locks are inherently less secure than PIN locks. Why?
From Android Security Internals: An In-Depth Guide to Android's Security by Nikolay Elenkov** ( runs a blog here )
.... the code for pattern unlock is entered by joining at least four points on a 3×3 matrix. Each point can be used only once (crossed points are disregarded) and the maximum number of points is nine. Internally, the pattern is stored as a byte sequence, with each point represented by its index, where 0 is top left and 8 is bottom right. Thus the pattern is similar to a PIN with a minimum of four and maximum of nine digits, which uses only nine distinct digits (0 to 8). However, because points cannot be repeated, the number of variations in an unlock pattern is considerably lower compared to those of a nine-digit PIN
**Screenshot of passage here
If you switch over to PIN , you can protect against smudge attacks by scrambling numbers as explained in my answer here either by using an app or Gravity Box Xposed module Marshmallow - disable unlock touch feedback