Log warning if null byte is detected in size field

rattail_corepos/corepos/importing/db/exporters/catapult_inventory.py

@@ -220,7 +220,9 @@ class InventoryItemImporter(FromCore, catapult_importing.model.InventoryItemImpo
         # TODO: this logic may actually be client-specific?  i just happened to
         # find some of these chars in a client DB and needed to avoid them, b/c
         # the openpyxl lib said IllegalCharacterError
-        if size is not None:
+        if size is not None and '\x00' in size:
+            log.warning("product %s has null byte in size field: %s",
+                        product.upc, product)
             size = size.replace('\x00', '')
 
         price_divider = None