After installing a zimlet I wrote, and despite the fact that it seems to be working correctly, I'm seeing a message like this in mailbox.log every time an email comes in:

2008-08-15 17:17:20,106 INFO  [LmtpServer-228] [ip=;] lmtp - Delivering message: size=2440 bytes, nrcpts=1,, msgid=<2740.20080>
2008-08-15 17:17:20,108 WARN  [LmtpServer-228] [;mid=10;] ParsedMessage - Unable to parse part 1 (, text/plain) of message with Message-ID <2740.20080815181706@wiia>.  Object will not be indexed.
com.zimbra.cs.object.ObjectHandlerException: error running ZimletHandler net_milodev_tiny
    at com.zimbra.cs.object.ObjectHandler.parse(
    at com.zimbra.cs.mime.MimeHandler.getObjects(
    at com.zimbra.cs.mime.MimeHandler.getDocument(
    at com.zimbra.cs.mime.ParsedMessage.analyzePart(
    at com.zimbra.cs.mime.ParsedMessage.analyzeBodyParts(
    at com.zimbra.cs.mime.ParsedMessage.analyzeNonBodyParts(
    at com.zimbra.cs.mime.ParsedMessage.analyzeFully(
    at com.zimbra.cs.mailbox.Mailbox.addMessage(
    at com.zimbra.cs.mailbox.Mailbox.addMessage(
    at com.zimbra.cs.filter.ZimbraMailAdapter.addMessage(
    at com.zimbra.cs.filter.ZimbraMailAdapter.doDefaultFiling(
    at com.zimbra.cs.filter.ZimbraMailAdapter.executeActions(
    at org.apache.jsieve.SieveFactory.evaluate(
    at com.zimbra.cs.filter.RuleManager.applyRules(
    at com.zimbra.cs.lmtpserver.ZimbraLmtpBackend.deliverMessageToLocalMailboxes(
    at com.zimbra.cs.lmtpserver.ZimbraLmtpBackend.deliver(
    at com.zimbra.cs.lmtpserver.LmtpHandler.processMessageData(
    at com.zimbra.cs.lmtpserver.TcpLmtpHandler.continueDATA(
    at com.zimbra.cs.lmtpserver.LmtpHandler.doDATA(
    at com.zimbra.cs.lmtpserver.LmtpHandler.processCommand(
    at com.zimbra.cs.lmtpserver.TcpLmtpHandler.processCommand(
    at com.zimbra.cs.tcpserver.ProtocolHandler.processConnection(
    at EDU.oswego.cs.dl.util.concurrent.PooledExecutor$ Source)
Caused by: com.zimbra.cs.zimlet.ZimletException: null regex value
    at com.zimbra.cs.zimlet.ZimletException.ZIMLET_HANDLER_ERROR(
    at com.zimbra.cs.zimlet.handler.RegexHandler.match(
    at com.zimbra.cs.object.ObjectHandler.parse(
    ... 24 more
The actual error varies slightly, but each time the "Caused by" message is the same - "com.zimbra.cs.zimlet.ZimletException: null regex value"

The only two references to regexes in my code are in the zimlet definition xml file, here:
<serverExtension hasKeyword="tinyurl" extensionClass="com.zimbra.cs.zimlet.handler.RegexHandler"/>
<contentObject type="tinyurl">
    <regex attrs="ig">http:\/\/\/(\w{6})</regex>
and the javascript file, here:
Net_Milodev_Tiny.prototype._getHtmlContent =
function(html, idx, obj, context) {
	var escapedUrl = obj.replace(/\"/g, '\"');
	if (escapedUrl.substr(0, 4) == 'www.') {
		escapedUrl = "http://" + escapedUrl + "/";
	html[idx++] = "<a target='_blank' href='";
	html[idx++] = escapedUrl;
	html[idx++] = "'>";
	html[idx++] = AjxStringUtil.htmlEncode(obj);
	html[idx++] = "</a>";
	return idx;
Sharp eyed observers will notice that I copied the last bit exactly from the com_zimbra_url zimlet, in order to get the tiny urls recognized to open in a new window, since I had to set the priority of this zimlet higher than the com_zimbra_url zimlet.

In searching the forums, I found 2 threads that obliquely reference similar problems, with no solutions (here and here).

Has anyone seen this before, or have an idea how to fix it? As I said, the zimlet appears to work correctly, but the errors are not exactly comforting.