Issue #3151993 by anmolgoyal74, huzooka, benjifisher, Wim Leers, quietone:...

Issue #3151993 by anmolgoyal74, huzooka, benjifisher, Wim Leers, quietone: Search settings migration (d7_search_settings) assumes that the search_default_module variable is always set

(cherry picked from commit 989fdedc)

core/modules/search/migrations/d7_search_settings.yml

@@ -7,7 +7,7 @@ source:
   plugin: variable
   constants:
     status: true
-  variables:
+  variables_no_row_if_missing:
     - minimum_word_size
     - overlap_cjk
     - search_cron_limit