From b3f9c4f93d78f3c81f46dbcce2a873701e158492 Mon Sep 17 00:00:00 2001
From: Tyler Goodlet <jgbt@protonmail.com>
Date: Tue, 3 May 2022 13:51:29 -0400
Subject: [PATCH] Only assert if input array actually has a size

---
 piker/data/_sharedmem.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/piker/data/_sharedmem.py b/piker/data/_sharedmem.py
index f1e89fca..8848ec1c 100644
--- a/piker/data/_sharedmem.py
+++ b/piker/data/_sharedmem.py
@@ -351,7 +351,7 @@ class ShmArray:
             # tries to access ``.array`` (which due to the index
             # overlap will be empty). Pretty sure we've fixed it now
             # but leaving this here as a reminder.
-            if prepend and update_first:
+            if prepend and update_first and length:
                 assert index < self._first.value
 
             if (