Re-add NULL constraint.

db/manifest

@@ -297,3 +297,4 @@ alter_genre_player_unique_constraint.sql
 musician_search.sql
 enhance_band_profile.sql
 alter_band_profile_rate_defaults.sql
+repair_band_profile.sql

db/up/repair_band_profile.sql

@@ -0,0 +1,3 @@
+ALTER TABLE musicians_instruments ALTER COLUMN player_id SET NOT NULL;
+ALTER TABLE performance_samples ALTER COLUMN player_id SET NOT NULL;
+ALTER TABLE online_presences ALTER COLUMN player_id SET NOT NULL;