Bug 161191 Null is inserted when drag columns to query text with ctrl key pressed
Description: Null is inserted when drag columns to query text with ctrl key pressed Steps to reproduce: 1. New a data source. 2. New a dataset. 3. Press and hold ctrl key, select OFFICECODE and CITY columns, drag to query text. Expected result: "CLASSICMODELS.OFFICES.OFFICECODE,CLASSICMODELS.OFFICES.CITY" is inserted in query text. Actual result: "null,CLASSICMODELS.OFFICES.OFFICECODE,CLASSICMODELS.OFFICES.CITY" is inserted
data/org.eclipse.birt.report.data.oda.jdbc.ui/src/org/eclipse/birt/report/data/oda/jdbc/ui/editors/SQLDataSetEditorPage.java
{
					
					Image image = tableImage;
							
					if ( tablesRs != null )
					{
						int numberOfTable;
						
						Preferences preferences = JdbcPlugin.getDefault( ).getPluginPreferences( );
						if ( preferences.contains( DateSetPreferencePage.USER_MAX_NUM_OF_TABLE_EACH_SCHEMA ) )
						{
							numberOfTable = preferences.getInt( DateSetPreferencePage.USER_MAX_NUM_OF_TABLE_EACH_SCHEMA );
						}
						else
						{
							numberOfTable = DateSetPreferencePage.DEFAULT_MAX_NUM_OF_TABLE_EACH_SCHEMA;
							preferences.setValue( DateSetPreferencePage.USER_MAX_NUM_OF_TABLE_EACH_SCHEMA,
									numberOfTable );
						}
						int count = 0;			
						
						while ( tablesRs.next( ) && count < numberOfTable)
						{