fix: handle nil member in MembershipFeeHelpers

- get_last_completed_cycle/2 and get_current_cycle/2 return nil when member is nil.
- Avoids FunctionClauseError when MemberLive.Show receives no member (e.g. after
  redirect or policy filter). Add unit tests for nil member.

lib/mv_web/helpers/membership_fee_helpers.ex

@@ -125,9 +125,11 @@ defmodule MvWeb.Helpers.MembershipFeeHelpers do
       iex> cycle = MvWeb.Helpers.MembershipFeeHelpers.get_last_completed_cycle(member)
       # => %MembershipFeeCycle{cycle_start: ~D[2024-01-01], ...}
   """
-  @spec get_last_completed_cycle(Member.t(), Date.t() | nil) :: MembershipFeeCycle.t() | nil
+  @spec get_last_completed_cycle(Member.t() | nil, Date.t() | nil) :: MembershipFeeCycle.t() | nil
   def get_last_completed_cycle(member, today \\ nil)
 
+  def get_last_completed_cycle(nil, _today), do: nil
+
   def get_last_completed_cycle(%Member{} = member, today) do
     today = today || Date.utc_today()
 
@@ -174,9 +176,11 @@ defmodule MvWeb.Helpers.MembershipFeeHelpers do
       iex> cycle = MvWeb.Helpers.MembershipFeeHelpers.get_current_cycle(member)
       # => %MembershipFeeCycle{cycle_start: ~D[2024-04-01], ...}
   """
-  @spec get_current_cycle(Member.t(), Date.t() | nil) :: MembershipFeeCycle.t() | nil
+  @spec get_current_cycle(Member.t() | nil, Date.t() | nil) :: MembershipFeeCycle.t() | nil
   def get_current_cycle(member, today \\ nil)
 
+  def get_current_cycle(nil, _today), do: nil
+
   def get_current_cycle(%Member{} = member, today) do
     today = today || Date.utc_today()
 

test/mv_web/helpers/membership_fee_helpers_test.exs

@@ -68,6 +68,11 @@ defmodule MvWeb.Helpers.MembershipFeeHelpersTest do
   end
 
   describe "get_last_completed_cycle/2" do
+    test "returns nil when member is nil" do
+      assert MembershipFeeHelpers.get_last_completed_cycle(nil) == nil
+      assert MembershipFeeHelpers.get_last_completed_cycle(nil, Date.utc_today()) == nil
+    end
+
     test "returns last completed cycle for member", %{actor: actor} do
       # Create test data
       fee_type =
@@ -184,6 +189,11 @@ defmodule MvWeb.Helpers.MembershipFeeHelpersTest do
   end
 
   describe "get_current_cycle/2" do
+    test "returns nil when member is nil" do
+      assert MembershipFeeHelpers.get_current_cycle(nil) == nil
+      assert MembershipFeeHelpers.get_current_cycle(nil, Date.utc_today()) == nil
+    end
+
     test "returns current cycle for member", %{actor: actor} do
       fee_type =
         Mv.MembershipFees.MembershipFeeType