Fix taint while deleting auras

How to reproduce: Create a new icon aura, rename it, move it to an existing dynamic group, duplicate it and delete the duplicate.

Error:
1x WeakAuras\WeakAuras-2.0.9.7-19-ge8def1e.lua:2819: attempt to index local 'v' (a string value)
WeakAuras\WeakAuras-2.0.9.7-19-ge8def1e.lua:2819: in function `Delete'
WeakAurasOptions\WeakAurasOptions-2.0.9.7-19-ge8def1e.lua:1173: in function `DeleteOption'
...eGUI-Widgets\AceGUIWidget-WeakAurasDisplayButton.lua:146: in function `func'
FrameXML\UIDropDownMenu.lua:748: in function `UIDropDownMenuButton_OnClick'
[string "*:OnClick"]:1: in function <[string "*:OnClick"]:1>