about no data columns

I have run forms in 6i it works fine but when run it in forms 9i it doesn't show me any errors but when i called exequetquery ctrl F11 it show me message unable to query with error no 40505 and also onother form ORA-01403 well i try to solve this i got that some of my column not have any value at detail block and i have use to summarise as a sum ot total to another field on that form
like this i have column insurance_rate in my table i what to sum this all records and put in to total_insurance and i sum to total_insurance on my form ,so i removed the this so error goes away but is i am write just tell me is I right in my apporoch or not or any thing i should i try

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