Patch by Sergei Golovan turns unnecessary error messages into debug messages.

Index: src/mod_caps.erl
===================================================================
--- src/mod_caps.erl	2009-04-01 17:23:51.000000000 +0200
+++ src/mod_caps.erl	2009-04-05 22:51:20.000000000 +0200
@@ -301,7 +301,7 @@
 		      end),
 		    gen_server:cast(self(), visit_feature_queries);
 		error ->
-		    ?ERROR_MSG("ID '~s' matches no query", [ID])
+		    ?DEBUG("ID '~s' matches no query", [ID])
 	    end;
 	{error, _} ->
 	    %% XXX: if we get error, we cache empty feature not to probe the client continuously
@@ -315,7 +315,7 @@
 		      end),
 		    gen_server:cast(self(), visit_feature_queries);
 		error ->
-		    ?ERROR_MSG("ID '~s' matches no query", [ID])
+		    ?DEBUG("ID '~s' matches no query", [ID])
 	    end;
 	    %gen_server:cast(self(), visit_feature_queries),
 	    %?DEBUG("Error IQ reponse from ~s:~n~p", [jlib:jid_to_string(From), SubEls]);