Don't hide 'undef' exceptions during config validation

src/ejabberd_config.erl

@@ -1083,7 +1083,7 @@ validate_opts(#state{opts = Opts} = State, ModOpts) ->
 						       [Opt, Error,
 							misc:format_val({yaml, Val})]),
 					    erlang:error(invalid_option);
-					  _:_ ->
+					  _:R when R /= undef ->
 					    ?ERROR_MSG("Invalid value for "
 						       "option '~s': ~s",
 						       [Opt, misc:format_val({yaml, Val})]),

src/ejabberd_listener.erl

@@ -586,7 +586,7 @@ validate_module_opt(Module, Opt, Val) ->
 	   catch _:_ -> listen_opt_type(Opt)
 	   end,
     try {Opt, VFun(Val)}
-    catch _:_ ->
+    catch _:R when R /= undef ->
 	    ?ERROR_MSG("Invalid value of listening option ~s: ~s",
 		       [Opt, misc:format_val({yaml, Val})]),
 	    erlang:error(badarg)

src/gen_mod.erl

@@ -620,7 +620,7 @@ validate_opt(Opt, Val, VFun) ->
 	NewVal -> [{Opt, NewVal}]
     catch {invalid_syntax, Error} ->
 	    err_invalid_option(Opt, Val, Error);
-	  _:_ ->
+	  _:R when R /= undef ->
 	    err_invalid_option(Opt, Val)
     end.