chore: fix grammatical issues in code comments (#1972)

* Update nullify.go

* Update export.go

* Update keys.go

Author: radik878

app/export.go

@@ -59,7 +59,7 @@ func (app *App) ExportAppStateAndValidators(forZeroHeight bool, jailAllowedAddrs
 //
 //nolint:gocyclo
 func (app *App) prepForZeroHeightGenesis(ctx sdk.Context, jailAllowedAddrs []string) {
-	// check if there is a allowed address list
+	// check if there is an allowed address list
 	applyAllowedAddrs := len(jailAllowedAddrs) > 0
 
 	allowedAddrsMap := make(map[string]bool)

app/keys.go

@@ -61,7 +61,7 @@ func (a *AppKeepers) GenerateKeys() {
 	a.memKeys = storetypes.NewMemoryStoreKeys(capabilitytypes.MemStoreKey)
 }
 
-// GetSubspace gets existing substore from keeper.
+// GetSubspace gets the existing substore from keeper.
 func (a *AppKeepers) GetSubspace(moduleName string) paramstypes.Subspace {
 	subspace, _ := a.ParamsKeeper.GetSubspace(moduleName)
 	return subspace

testutil/nullify/nullify.go

@@ -13,7 +13,7 @@ var (
 	coinsType = reflect.TypeOf(sdk.Coins{})
 )
 
-// Fill analyze all struct fields and slices with
+// Fill analyzes all struct fields and slices with
 // reflection and initialize the nil and empty slices,
 // structs, and pointers.
 func Fill(x interface{}) interface{} {