Only announce if bc has names

Signed-off-by: Rahix <rahix@rahix.de>

bc.lua

@@ -148,11 +148,14 @@ function BaseControl:finalize(waits, timeout)
   end
 
   -- Announce own nouns and verbs
+  local nouns, verbs = self:nouns(true), self:verbs(true)
+  if #nouns > 0 or #verbs > 0 then
     self.network:broadcast{
       ty=Message.Register,
-    nouns=self:nouns(true),
+      nouns=nouns,
-    verbs=self:verbs(true),
+      verbs=verbs,
     }
+  end
 
   if #(waits or {}) ~= 0 then
     -- Wait for requested names