Random-seeming "Uncaught exception escaped" with no reference to my code

Every so often, while running in Dev Mode, I'll get this exception (or something like it). Is this some under the hood local-only issue I don't need to worry about, or does it hint as something I should fix?  Is there anything I can do about it?

Uncaught exception escaped

com.google.gwt.dev.shell.HostedModeException: Something other than an int was returned from JSNI method '@com.google.gwt.query.client.js.JsCache::length()': JS value of type boolean, expected int

    at com.google.gwt.dev.shell.JsValueGlue.getIntRange(JsValueGlue.java:266)

    at com.google.gwt.dev.shell.JsValueGlue.get(JsValueGlue.java:144)

    at com.google.gwt.dev.shell.ModuleSpace.invokeNativeInt(ModuleSpace.java:247)

    at com.google.gwt.dev.shell.JavaScriptHost.invokeNativeInt(JavaScriptHost.java:75)

    at com.google.gwt.query.client.js.JsCache$.length$(JsCache.java)

    at com.google.gwt.query.client.js.JsObjectArray$.length$(JsObjectArray.java:52)

    at com.google.gwt.query.client.plugins.events.EventsListener.dispatchEvent(EventsListener.java:372)

    at com.google.gwt.query.client.plugins.events.EventsListener.onBrowserEvent(EventsListener.java:435)

    at com.google.gwt.user.client.DOM.dispatchEventImpl(DOM.java:1351)

    at com.google.gwt.user.client.DOM.dispatchEvent(DOM.java:1307)

    at sun.reflect.GeneratedMethodAccessor65.invoke(Unknown Source)

    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

    at java.lang.reflect.Method.invoke(Method.java:597)

    at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)

    at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)

    at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)

    at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessagesWhileWaitingForReturn(BrowserChannelServer.java:337)

    at com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:218)

    at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:136)

    at com.google.gwt.dev.shell.ModuleSpace.invokeNative(ModuleSpace.java:561)

    at com.google.gwt.dev.shell.ModuleSpace.invokeNativeObject(ModuleSpace.java:269)

    at com.google.gwt.dev.shell.JavaScriptHost.invokeNativeObject(JavaScriptHost.java:91)

    at com.google.gwt.core.client.impl.Impl.apply(Impl.java)

    at com.google.gwt.core.client.impl.Impl.entry0(Impl.java:213)

    at sun.reflect.GeneratedMethodAccessor60.invoke(Unknown Source)

    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

    at java.lang.reflect.Method.invoke(Method.java:597)

    at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)

    at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)

    at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)

    at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessages(BrowserChannelServer.java:292)

    at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:546)

    at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:363)

    at java.lang.Thread.run(Thread.java:662)

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