Problem: panic when store not exists in historical version

Solution:
- make a dummy store, so client get empty data instead of panic on nil pointer

CHANGELOG.md

@@ -38,6 +38,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 ## [Unreleased]
 
 * (x/staking) Fix a possible bypass of delagator slashing: [GHSA-86h5-xcpx-cfqc](https://github.com/cosmos/cosmos-sdk/security/advisories/GHSA-86h5-xcpx-cfqc)
+* (store) Fix a nil pointer panic when query historical state where a new store don't exist.
 
 ## [v0.47.11](https://github.com/cosmos/cosmos-sdk/releases/tag/v0.47.11) - 2024-04-22
 

store/rootmulti/store.go

@@ -539,6 +539,11 @@ func (rs *Store) CacheMultiStoreWithVersion(version int64) (types.CacheMultiStor
 				}
 			}
 
+			if cacheStore == nil {
+				// when loading a historical version, the store might not exists yet.
+				cacheStore = dbadapter.Store{DB: dbm.NewMemDB()}
+			}
+
 		default:
 			cacheStore = store
 		}