Naughty: Handle invalid UTF-8 more sanely

Previously, if setting the textbox's text failed this caused more problems later
on. This commit makes sure that an invalid text never breaks pango.

Signed-off-by: Uli Schlachter <psychon@znc.in>

lib/naughty.lua.in

@@ -365,7 +365,9 @@ function notify(args)
     -- (Setting a textbox' .text to an invalid pattern throws a lua error)
     if not pcall(setText, "<br.->", "\n") then
         -- That failed, escape everything which might cause an error from pango
-        setText("[<>&]", { ['<'] = "&lt;", ['>'] = "&gt;", ['&'] = "&amp;" })
+        if not pcall(setText, "[<>&]", { ['<'] = "&lt;", ['>'] = "&gt;", ['&'] = "&amp;" }) then
+            textbox.text = "<i>&lt;Invalid markup, cannot display message&gt;</i>"
+        end
     end
 
     -- create iconbox