Always reset persister in handler

Reviewed-on: urdt/ussd#179
Reviewed-by: Alfred Kamanda <alfredkamandamw@gmail.com>

internal/handlers/ussd/menuhandler.go

@@ -114,6 +114,9 @@ func (h *Handlers) Init(ctx context.Context, sym string, input []byte) (resource
 		logg.WarnCtxf(ctx, "handler init called before it is ready or more than once", "state", h.st, "cache", h.ca)
 		return r, nil
 	}
+	defer func() {
+		h.pe = nil
+	}()
 
 	h.st = h.pe.GetState()
 	h.ca = h.pe.GetMemory()
@@ -133,7 +136,6 @@ func (h *Handlers) Init(ctx context.Context, sym string, input []byte) (resource
 		logg.ErrorCtxf(ctx, "perister fail in handler", "state", h.st, "cache", h.ca)
 		return r, fmt.Errorf("cannot get state and memory for handler")
 	}
-	h.pe = nil
 
 	logg.DebugCtxf(ctx, "handler has been initialized", "state", h.st, "cache", h.ca)