Add guard clause to check if table exists

This should solve one of the reasons deploying to staging fails. re: duplicat table rancher error from db-setup

db/migrate/20221205210847_create_iiif_print_derivative_attachments.iiif_print.rb

@@ -1,13 +1,15 @@
 # This migration comes from iiif_print (originally 20181214181358)
 class CreateIiifPrintDerivativeAttachments < ActiveRecord::Migration[5.0]
   def change
-    create_table :iiif_print_derivative_attachments do |t|
-      t.string :fileset_id
-      t.string :path
-      t.string :destination_name
+    unless unless table_exists?(:iiif_print_derivative_attachments) 
+      create_table :iiif_print_derivative_attachments do |t|
+        t.string :fileset_id
+        t.string :path
+        t.string :destination_name
 
-      t.timestamps
+        t.timestamps
+      end
+      add_index :iiif_print_derivative_attachments, :fileset_id
     end
-    add_index :iiif_print_derivative_attachments, :fileset_id
   end
 end