fix: signature window failing when trigger context empty

Author: Saghen

lua/blink/cmp/init.lua

@@ -75,7 +75,7 @@ cmp.setup_signature_help = function()
   signature_trigger.listen_on_show(function(context)
     cmp.sources.cancel_signature_help()
     cmp.sources.get_signature_help(context, function(signature_help)
-      if signature_help ~= nil and signature_trigger.context.id == context.id then
+      if signature_help ~= nil and signature_trigger.context ~= nil and signature_trigger.context.id == context.id then
         signature_trigger.set_active_signature_help(signature_help)
         signature_window.open_with_signature_help(context, signature_help)
       else