Bug 142939 Invalid interval will cause incorrect group action.
Description: Invalid interval will cause incorrect group action. Steps to reproduce: 1. Insert a list 2. Add a group, key is string type column, set interval to year, range to 3 3. Preview Expected result: Error msg about invald interval and ignore the invalid interval. Actual result: No error msg and only return one group with all datarows.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/impl/QueryExecutor.java
* Creates a subscope within parent scope
	 * @param parentAndProtoScope parent scope. If null, the shared top-level scope is used as parent
	 */
	private Scriptable newSubScope( Scriptable parentAndProtoScope )
	{
		if ( parentAndProtoScope == null )
			parentAndProtoScope = sharedScope;
		Context cx = Context.enter( );
		try
		{
			Scriptable scope = cx.newObject( parentAndProtoScope );
			scope.setParentScope( parentAndProtoScope );
			scope.setPrototype( parentAndProtoScope );
			return scope;
		}
		finally
		{
			Context.exit( );
		}
	}
	/*
	 * @see org.eclipse.birt.data.engine.impl.IQueryExecutor#getNestedLevel()
	 */
	public int getNestedLevel( )
	{
		return this.nestedLevel;
	}
	/*
	 * @see org.eclipse.birt.data.engine.impl.IQueryExecutor#getDataSourceInstanceHandle()
	 */