Bug 182673 No default value error message prompts incorrectly
Steps to reproduce: 1. New a report parameter; 2. Choose control type as Combo; 3. Choose parameter as dynamic type; Expected result: As the isRequired is false by default, parameter's default value can be null value. There should be no error message about no default value prompt. Actual result; Error messages prompts
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/ui/dialogs/CascadingParametersDialog.java
selectedParameter.setName( UIUtil.convertToModelString( paramNameEditor.getText( ),
					true ) );
			selectedParameter.setCategory( formatCategroy );
			selectedParameter.setPattern( formatPattern );
			refreshValueTable( );
		};
	}
	private boolean isSingle( )
	{
		return singleDataSet.getSelection( );
	}
	private ScalarParameterHandle getFirstParameter( )
	{
		if ( inputParameterGroup.getParameters( ).getCount( ) > 0 )
		{
			return (ScalarParameterHandle) inputParameterGroup.getParameters( )
					.get( 0 );
		}
		return newParameter;
	}
	private boolean checkParameter( ScalarParameterHandle paramHandle )
	{
		if ( paramHandle.getValueExpr( ) == null
				|| getColumnName( paramHandle, COLUMN_VALUE ) == null )
		{
			return false;
		}
		return true;
	}
}