Handle more than 2 panes

[boobatron]

Description

With 3 similar configuration files open in 3 panes, scroll-sync throws an error

Steps to Reproduce

1. Open 3 text files in 3 panes
2. Click Packages > Toggle Scroll Sync

Expected behavior:

Synchronise the 3 (or more) scroll bars.

Actual behavior:

Error thrown.

Reproduces how often: 100%

Versions

MS Windows 11 Home x64 Version 10.0.22621 Build 22621

Atom : 1.60.0 Electron: 9.4.4 Chrome : 83.0.4103.122 Node : 12.14.1

apm 2.6.2 npm 6.14.13 node 12.14.1 x64 atom 1.60.0 python git visual studio