BINGO. I was able to get an actual error by selecting the component in the React devtools and doing $r.setState({queryDone: true}).
react.browserify.js:
_updateRenderedComponent: function(transaction, context) {
var prevComponentInstance = this._renderedComponent;
var prevRenderedElement = prevComponentInstance._currentElement; // ERROR HERE
var childContext = this._getValidatedChildContext();
var nextRenderedElement = this._renderValidatedComponent(childContext);
Error:
Uncaught TypeError: Cannot read property ‘_currentElement’ of null(…)
It concerns me that React didn’t throw an error in the console, until I ran setState manually.