Add a test for safe_jsonb_set

test/safe_jsonb_set_test.exs

@@ -0,0 +1,12 @@
+defmodule Pleroma.SafeJsonbSetTest do
+  use Pleroma.DataCase
+
+  test "it doesn't wipe the object when asked to set the value to NULL" do
+    assert %{rows: [[%{"key" => "value", "test" => nil}]]} =
+             Ecto.Adapters.SQL.query!(
+               Pleroma.Repo,
+               "select safe_jsonb_set('{\"key\": \"value\"}'::jsonb, '{test}', NULL);",
+               []
+             )
+  end
+end