bplist: Check for invalid offset_size in bplist trailer
diff --git a/src/bplist.c b/src/bplist.c
index 881c2c8..4a00683 100644
--- a/src/bplist.c
+++ b/src/bplist.c
@@ -733,6 +733,9 @@
     if (num_objects == 0)
         return;
 
+    if (offset_size == 0)
+        return;
+
     if (root_object >= num_objects)
         return;