Was acting on the wrong table!

sql/patch_45_46_c.sql

@@ -5,7 +5,7 @@
 # description:
 # Make external_db column in unmapped_object be SMALLINT UNSIGNED explicitly.
 
-ALTER TABLE external_db CHANGE COLUMN external_db_id external_db_id SMALLINT UNSIGNED;
+ALTER TABLE unmapped_object CHANGE COLUMN external_db_id external_db_id SMALLINT UNSIGNED;
 
 # patch identifier
 INSERT INTO meta (meta_key, meta_value) VALUES ('patch', 'patch_45_46_c.sql|unmapped_object.external_db_id');