Composite: Raises "global failure" in Opera

[j-ulrich]

Running multiple test files using composite raises a "global failure" in Opera (I am using Opera version 12.02 on Windows):

Uncaught exception: TypeError: Cannot convert 'iframeWin.QUnit' to object
in qunit-composite.js, Line 37

To reproduce, simply run the composite-demo-test.html in Opera.

The problem seems to be that the load event is fired shortly after the iframe is inserted into the DOM but at that time, the src attribute is still empty, hence, no QUnit object exists in the iframe's window object. The load event is then fired again when the src attribute has been changed and the test file was loaded.