changing project directory leads to "Cannot read property 'overlay' of unde

Earlier today i changed my project’s directory out of Dropbox due to Dropbox synch issues. I just dragged and dropped my whole project directory to a new parent directory. I then deleted the ‘node_module’ directory, ran maven clean, and did the following steps.

  1. npm install
  2. Maven command vaadin:prepare-frontend
  3. Mavec command vaadin:build-frontend

All those steps ran successfully. The application starts up. But when I goto the site locally I now get this error when I click on one of the links:

(TypeError) : Cannot read property 'overlay' of undefined

Any ideas what the issue could be?

Here is the error from the console:

vaadin-6-96b14fcf4fc71a31122f.cache.js:1 Uncaught TypeError: Cannot read property 'overlay' of undefined
    at HTMLElement.eval (eval at <anonymous> (vaadin-6-96b14fcf4fc71a31122f.cache.js:1), <anonymous>:3:29)
    at Object.eval (eval at <anonymous> (vaadin-6-96b14fcf4fc71a31122f.cache.js:1), <anonymous>:3:62)
    at vaadin-6-96b14fcf4fc71a31122f.cache.js:1
    at ul (vaadin-6-96b14fcf4fc71a31122f.cache.js:1)
    at vaadin-6-96b14fcf4fc71a31122f.cache.js:1
    at na (vaadin-6-96b14fcf4fc71a31122f.cache.js:1)
    at gi.Bl.Z (vaadin-6-96b14fcf4fc71a31122f.cache.js:1)
    at Gf (vaadin-6-96b14fcf4fc71a31122f.cache.js:1)
    at _l (vaadin-6-96b14fcf4fc71a31122f.cache.js:1)
    at $a.Bl.A (vaadin-6-96b14fcf4fc71a31122f.cache.js:1)
    at zo (vaadin-6-96b14fcf4fc71a31122f.cache.js:1)
    at Dl (vaadin-6-96b14fcf4fc71a31122f.cache.js:1)
    at Cl (vaadin-6-96b14fcf4fc71a31122f.cache.js:1)
    at Qn.Bl.tb (vaadin-6-96b14fcf4fc71a31122f.cache.js:1)
    at qt.Bl.H (vaadin-6-96b14fcf4fc71a31122f.cache.js:1)
    at XMLHttpRequest.<anonymous> (vaadin-6-96b14fcf4fc71a31122f.cache.js:1)
    at cr (vaadin-6-96b14fcf4fc71a31122f.cache.js:1)
    at pf (vaadin-6-96b14fcf4fc71a31122f.cache.js:1)
    at XMLHttpRequest.<anonymous> (vaadin-6-96b14fcf4fc71a31122f.cache.js:1)