Don't delete account with avatar

Fixes #200

migrations/2018-09-07-212003_fix_avatar_deletion/down.sql

@@ -0,0 +1,7 @@
+-- This file should undo anything in `up.sql`
+ALTER TABLE users
+    DROP CONSTRAINT users_avatar_id_fkey,
+    ADD CONSTRAINT users_avatar_id_fkey
+    FOREIGN KEY (avatar_id)
+    REFERENCES medias(id)
+    ON DELETE CASCADE;

migrations/2018-09-07-212003_fix_avatar_deletion/up.sql

@@ -0,0 +1,7 @@
+-- Your SQL goes here
+ALTER TABLE users
+    DROP CONSTRAINT users_avatar_id_fkey,
+    ADD CONSTRAINT users_avatar_id_fkey
+    FOREIGN KEY (avatar_id)
+    REFERENCES medias(id)
+    ON DELETE SET NULL;