mute: fix issue with not being able to change mute duration

This patch fixes an issue where the user can’t change the mute duration
when adding a new mute item.

The problem was that `expiration` was nil for indefinite which isn’t
really allowed for a Picker.

I fixed this by adding an indefinite case to DamusDuration.

Closes: https://github.com/damus-io/damus/issues/1907
Lighting-address: fishcharlie@strike.me
Signed-off-by: Charlie Fish <contact@charlie.fish>
Reviewed-by: William Casarin <jb55@jb55.com>
Signed-off-by: William Casarin <jb55@jb55.com>

damus/Types/DamusDuration.swift

@@ -8,12 +8,15 @@
 import Foundation
 
 enum DamusDuration: CaseIterable {
+    case indefinite
     case day
     case week
     case month
 
     var title: String {
         switch self {
+        case .indefinite:
+            return NSLocalizedString("Indefinite", comment: "Mute a given item indefinitly (until user unmutes it). As opposed to muting the item for a given period of time.")
         case .day:
             return NSLocalizedString("24 hours", comment: "A duration of 24 hours/1 day to be shown to the user. Most likely in the context of how long they want to mute a piece of content for.")
         case .week:
@@ -27,6 +30,8 @@ enum DamusDuration: CaseIterable {
         let current_date = Date()
 
         switch self {
+        case .indefinite:
+            return nil
         case .day:
             return Calendar.current.date(byAdding: .day, value: 1, to: current_date)
         case .week:

damus/Views/Muting/AddMuteItemView.swift

@@ -9,7 +9,7 @@ import SwiftUI
 struct AddMuteItemView: View {
     let state: DamusState
     @State var new_text: String = ""
-    @State var expiration: DamusDuration?
+    @State var expiration: DamusDuration = .indefinite
 
     @Environment(\.dismiss) var dismiss
 
@@ -23,7 +23,6 @@ struct AddMuteItemView: View {
                 .padding(.bottom)
 
             Picker(selection: $expiration) {
-                Text("Indefinite", comment: "Mute a given item indefinitly (until user unmutes it). As opposed to muting the item for a given period of time.")
                 ForEach(DamusDuration.allCases, id: \.self) { duration in
                     Text(duration.title).tag(duration)
                 }
@@ -55,7 +54,7 @@ struct AddMuteItemView: View {
             .cornerRadius(10)
 
             Button(action: {
-                let expiration_date: Date? = self.expiration?.date_from_now
+                let expiration_date: Date? = self.expiration.date_from_now
                 let mute_item: MuteItem? = {
                     if new_text.starts(with: "npub") {
                         if let pubkey: Pubkey = bech32_pubkey_decode(new_text) {