Use exceptions.

src/XMPPIQ.m

@@ -34,14 +34,20 @@
 - initWithType: (OFString*)type_
 	    ID: (OFString*)ID_
 {
-	if (![type_ isEqual: @"get"] &&
-	    ![type_ isEqual: @"set"] &&
-	    ![type_ isEqual: @"result"] &&
-	    ![type_ isEqual: @"error"])
-		of_log(@"Invalid IQ type!");
-
-	return [super initWithName: @"iq"
+	self = [super initWithName: @"iq"
 			      type: type_
 				ID: ID_];
+
+	@try {
+		if (![type_ isEqual: @"get"] && ![type_ isEqual: @"set"] &&
+		    ![type_ isEqual: @"result"] && ![type_ isEqual: @"error"])
+			@throw [OFInvalidArgumentException newWithClass: isa
+							       selector: _cmd];
+	} @catch (id e) {
+		[self release];
+		@throw e;
+	}
+
+	return self;
 }
 @end