Check if Schema has been defined

[willmustafa]

The Problem: Some Magento XML gets an error in the line this.element = schema.elements[nsName.name]; because schema is undefined.

The Solution: Simple check if schema has been defined if(schema) this.element = schema.elements[nsName.name];

Tests: All existing tests passed. I didn't create a new test because all worked well and new tests would be the same.