In ScrollBar_Scroll(): Terminate immediately if the ScrollBar is hidden.

diff --git a/Frame.lua b/Frame.lua
index 2464407..ad13493 100644
--- a/Frame.lua
+++ b/Frame.lua
@@ -2784,6 +2784,9 @@ do
 	highlight._texture:SetAllPoints(highlight)

 	local function ScrollBar_Scroll(delta)
+		if not ScrollBar:IsShown() then
+			return
+		end
 		local cur_val = ScrollBar:GetValue()
 		local min_val, max_val = ScrollBar:GetMinMaxValues()