fix: always check if StateSearchMessage returns nil

It returns nil on "not found".

Fixes the cases not covered in:
https://github.com/filecoin-project/lotus/pull/6787

cli/state.go

@@ -446,6 +446,9 @@ var StateExecTraceCmd = &cli.Command{
 		if err != nil {
 			return err
 		}
+		if lookup == nil {
+			return fmt.Errorf("failed to find message: %s", mcid)
+		}
 
 		ts, err := capi.ChainGetTipSet(ctx, lookup.TipSet)
 		if err != nil {
@@ -1491,6 +1494,10 @@ var StateSearchMsgCmd = &cli.Command{
 			return err
 		}
 
+		if mw == nil {
+			return fmt.Errorf("failed to find message: %s", msg)
+		}
+
 		m, err := api.ChainGetMessage(ctx, msg)
 		if err != nil {
 			return err