Fix dispel border toggles breaking the debuffs and dispels indicators

[KharchenkoDmitriy]

The "Show dispel-type border" (debuffs) and "Show frame border" (dispels) checkbuttons fire UpdateIndicators with setting == "checkbutton", but neither UnitButton_*.lua's UpdateIndicators had a branch for them, so both fell through to the catch-all:

indicatorBooleans[indicatorName] = value2

For debuffs that clobbers the dispellableByMe filter, so ticking the box silently hid every debuff the player cannot dispel. For dispels it is worse: indicatorBooleans["dispels"] holds the filter table, so replacing it with a boolean makes the next aura update error out on indicatorBooleans["dispels"]["dispellableByMe"] and the whole indicator stops working. Neither toggle actually reached the border it names.

Handle both explicitly instead:

• showDispelBorder re-applies the icon border thickness (0 when off), which takes effect immediately on the existing icons.
• showDispelFrameBorder flips the dispels frame-border flag and forces an aura update, since the border strips are only colored and shown from SetDispels -- turning the toggle back on would otherwise do nothing visible until the unit's auras next changed.

Applied to all flavors: UnitButton.lua, UnitButton_Cata_Wrath.lua, UnitButton_Mists.lua and UnitButton_Vanilla.lua (also used by TBC).

[KharchenkoDmitriy]

There was also thikness slider issue

1x Cell/RaidFrames/UnitButton_Vanilla.lua:714: attempt to index local 'indicator' (a nil value)
[Cell/RaidFrames/UnitButton_Vanilla.lua]:714: in function 'func'
[Cell/Utils.lua]:942: in function 'IterateAllUnitButtons'
[Cell/RaidFrames/UnitButton_Vanilla.lua]:712: in function 'onEventFunc'
[Cell/Libs/CallbackHandler.lua]:24: in function 'Fire'
[Cell/Modules/Indicators/Indicators.lua]:2185: in function 'thicknessFunc'
[Cell/Widgets/Widgets_IndicatorSettings.lua]:663: in function 'afterValueChangedFn'
[Cell/Widgets/Widgets.lua]:1220: in function <Cell/Widgets/Widgets.lua:1210>

Included the fix