fix: support x/collection migration on old chains (#1106)

* Support old chains

* Update CHANGELOG.md

* Add comment

CHANGELOG.md

@@ -65,6 +65,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 * (ostracon) [\#1099](https://github.com/Finschia/finschia-sdk/pull/1099) feat!: remove libsodium vrf library.
 * (x/collection) [\#1102](https://github.com/finschia/finschia-sdk/pull/1102) Reject modifying NFT class with token index filled in MsgModify
 * (x/collection) [\#1105](https://github.com/Finschia/finschia-sdk/pull/1105) Add minted coins to balance in x/collection MsgMintFT
+* (x/collection) [\#1106](https://github.com/Finschia/finschia-sdk/pull/1106) Support x/collection migration on old chains
 
 ### Build, CI
 * (build,ci) [\#1043](https://github.com/Finschia/finschia-sdk/pull/1043) Update golang version to 1.20

x/collection/keeper/migrations/v2/store.go

@@ -91,7 +91,9 @@ func updateContractFTStatistics(store storetypes.KVStore, contractID string, sup
 		return err
 	}
 
-	for intClassID := uint64(1); intClassID < nextClassIDs.Fungible.Uint64(); intClassID++ {
+	// In the old chains, classID of fungible tokens starts from zero
+	// In the new chains, it starts from one, but it does not hurts because amount of zero is not set to the store.
+	for intClassID := uint64(0); intClassID < nextClassIDs.Fungible.Uint64(); intClassID++ {
 		classID := fmt.Sprintf("%08x", intClassID)
 
 		// update supply
@@ -104,6 +106,7 @@ func updateContractFTStatistics(store storetypes.KVStore, contractID string, sup
 			}
 			store.Set(supplyKey, bz)
 		} else {
+			supply = sdk.ZeroInt()
 			store.Delete(supplyKey)
 		}