Bug 121687 Exception throws when export data in table which inside a grid cell.
Description: Exception throws when export data in table which inside a grid cell. Steps to reproduce: 1. insert a grid. 2. insert one table to one grid cell. 3. insert another table to the other grid cell. 4. export data in two tables. Expected result: Data are exported. Actual result: Exception in: ReportEngineService.getMetaData( )
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/api/impl/DataExtractionTask.java
Iterator iter = exprs.iterator( );
				while ( iter.hasNext( ) )
				{
					IScriptExpression expr = (IScriptExpression) iter.next( );
					if ( expr.getText( ).equalsIgnoreCase( selectedColumns[i] ) )
					{
						findColumn = true;
						break;
					}
				}
				if ( findColumn == false )
				{
					throw new EngineException( "Invalid Columns" );
				}
			}
		}
		else
		{
			selectedColumns = new String[exprs.size( )];
			Iterator iter = exprs.iterator( );
			
			for ( int i = 0; i < selectedColumns.length; i++ )
			{
				IScriptExpression expr = (IScriptExpression) iter.next( );
				selectedColumns[i] = expr.getText( );
			}
		}
 	}
}