The value "" is not in the map

I have created a report using RDP class. I want to open it from the form LedgerJournalTable by selecting one line from grid and clicking the menu item. I have also written the controller class to achieve this, but when I click on the menu item, it gives the error that the value "" is not in the map.
After debugging, I found that this line this.setRanges(this.parmReportContract().parmQueryContracts().lookup(this.getFirstQueryContractKey())); in the function protected void prePromptModifyContract() gives the error. Please help. I have not created query and I don't want to use it.