Added a nil bailout in UpdatePlugin (bad mikma)

diff --git a/NinjaPanel.lua b/NinjaPanel.lua
index dfad0b1..920e383 100644
--- a/NinjaPanel.lua
+++ b/NinjaPanel.lua
@@ -253,7 +253,7 @@ function NinjaPanel:UpdatePlugin(event, name, key, value, dataobj)
 	local button = entry.button

 	if key == "text" then
-		button.text:SetFormattedText("%s", value)
+		button.text:SetFormattedText("%s", value or "")
 		self:UpdateButtonWidth(button)
 	elseif key == "icon" then
 		button.icon:SetTexture(value)