Fix
change line 165 in Warfront.lua to
local length = tbl.Alliance.scenario[1]

Describe the bug
attempting to access the databroker dropdown for SavedInstances throws the above error.

Do you have an error log of what happened?
3x SavedInstances\Warfront.lua:165: attempt to concatenate local 'length' (a table value)
SavedInstances\Warfront.lua:165: in function ShowTooltip' SavedInstances\SavedInstances-8.2.1-6-g84ecc51.lua:3931: in function ShowTooltip'
SavedInstances\SavedInstances-8.2.1-6-g84ecc51.lua:2626: in function OnEnter' Bazooka\Bazooka-v2.8.10.lua:1582: in function showTip'
Bazooka\Bazooka-v2.8.10.lua:1387: in function <Bazooka\Bazooka.lua:1378>

Which version of SavedInstances are you using?
8.2.1-6-g84ecc51-alpha