Provision or Reserve for bad debts is not an expense. Please first understand what is the nature of a provision. When we are uncertain about the amount or timing of any liability or expense, we set apart an estimated amount from the Profit & Loss A/c. The journal entry for that is:
Profit & Loss A/c Dr.
To Provision for Bad Debts A/c
So when actual bad debts happen, they are not debited to Profit & Loss A/c but they are debited to Provisition for Bad Debts A/c, entry for that is:
Provision for Bad Debts A/c Dr.
To Bad Debts A/c
You may notice from above that Provision for Bad Debts has a credit balance. An account with a credit balance is transferred to the credit side of any account. This is the reason it is transferred to the credit side of Realisation A/c at the time of dissolution. An account with debit balance is always transferred to the debit side of another account. For example Sr. Debtors A/c is a debit balance and that is transferred to the debit side of the Realisation.