FIX: Reset general_category_id if the general category was deleted (#18634)

On sites that were seeded with a general category id and that category
was deleted prior to the fix in efb116d2bd
this migration will reset the SiteSetting.general_category_id back to
the default because there is no longer a corresponding category for it.

This is to fix a composer bug that occurs if there is a
SiteSetting.general_category_id value present that doesn't match an
existing category.

db/migrate/20221017223309_fix_general_category_id.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+## If the *new* seeded General category was deleted before
+# commit efb116d2bd4d1e02df9ddf79316112e0555b4c1e the site will need this migration
+# to reset the general_category_id setting.
+
+class FixGeneralCategoryId < ActiveRecord::Migration[7.0]
+  def up
+    general_category_id = DB.query_single("SELECT value FROM site_settings WHERE name = 'general_category_id'")
+    return if general_category_id.blank? || general_category_id[0].to_i < 0
+    matching_category_id = DB.query_single("SELECT id FROM categories WHERE id = #{general_category_id[0]}")
+
+    # If the general_category_id has been set to something other than the default and there isn't a matching
+    # category to go with it we should set it back to the default.
+    if general_category_id[0].to_i > 0 && matching_category_id.blank?
+      execute "UPDATE site_settings SET value = '-1', updated_at = now() WHERE name = 'general_category_id';"
+    end
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+end