Bug 206285 Rename the report contain parameter will lead to the report cannot be preview[0705]
Description: Rename the report will lead to the report cannot be preview[0705] Step: 1. New a report contain a parameter named R1. 2. Preview it. 3. Rename the report as R2 4. Preview it again. Actual result: Step 2 is ok. But the step 4 will pop up an error and said that the report does not exist or contains errors. Expected result: The report can be preview when rename it.
UI/org.eclipse.birt.report.designer.ui.preview.web/src/org/eclipse/birt/report/designer/ui/preview/editors/ReportPreviewFormPage.java
String exprVarName = varName + "_" 
										+ PROP_EXPR + "_"; 
								ConfigVariable exprVar = handle
										.findConfigVariable( exprVarName );
								String expr = parameter.getValueExpr( );
								String cachedExpr = null;
								if ( exprVar != null )
									cachedExpr = exprVar.getValue( );
								if ( cachedExpr == null )
									cachedExpr = ""; 
								if ( expr == null )
									expr = ""; 
								
								if ( !cachedExpr.equals( expr ) )
									continue;
							}
							if ( paramName != null && paramName.length( ) > 0 )
							{
								if ( DesignChoiceConstants.SCALAR_PARAM_TYPE_MULTI_VALUE
										.equalsIgnoreCase( parameter
												.getParamType( ) ) )
								{
									
									List values = (List) configVars
											.get( paramName );
									if ( values == null )
									{
										values = new ArrayList( );
										configVars.put( paramName, values );