Bug 148951 Wrong error msg when set nonexisted col as group key
Description: Wrong error msg when set nonexisted col as group key Steps to reproduce: 1. Insert a table, bind it to dataset 2. Add a group, input abc as group key which is invalid. 3. Preview Expected result: Friendly error msg to tell user the group key is wrong. Actual result: + Group key "abc" in group 1 cannot depend on column bindings defined in the group lower than itself. data.engine.InvalidGroupKey ( 1 time(s) ) detail : org.eclipse.birt.data.engine.core.DataException: Group key "OUNTR" in group 1 cannot depend on column bindings defined in the group lower than itself.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/impl/ExprManagerUtil.java
String getValue( )
		{
			return this.value;
		}
		/**
		 * @param n
		 */
		void addChild( Node n )
		{
			this.children.add( n );
		}
		/** 
		 * @return
		 */
		List getChildren( )
		{
			return this.children;
		}
		/*
		 * @see java.lang.Object#equals(java.lang.Object)
		 */
		public boolean equals( Object o )
		{
			if ( ( o instanceof Node ) && ( (Node) o ).value.equals( this.value ) )
				return true;
			return false;
		}		
	}
	
}