Use placeholder when provider logo is missing

So far it's what happens for dynamically added providers, because
there is no local asset.

Passepartout-iOS/Global/SwiftGen+Assets.swift

@@ -284,6 +284,7 @@ internal enum Asset {
     internal static let mullvad = ImageAsset(name: "mullvad")
     internal static let nordvpn = ImageAsset(name: "nordvpn")
     internal static let pia = ImageAsset(name: "pia")
+    internal static let placeholder = ImageAsset(name: "placeholder")
     internal static let protonvpn = ImageAsset(name: "protonvpn")
     internal static let tunnelbear = ImageAsset(name: "tunnelbear")
     internal static let vyprvpn = ImageAsset(name: "vyprvpn")

Passepartout-iOS/Global/Theme.swift

@@ -191,7 +191,7 @@ extension MFMailComposeViewController {
 
 // FIXME: load from index JSON
 extension Infrastructure.Metadata {
-    var logo: UIImage? {
+    var logo: UIImage {
         return ImageAsset(name: name.lowercased()).image
     }
 }

Passepartout-iOS/Providers.xcassets/placeholder.imageset/Contents.json

@@ -0,0 +1,22 @@
+{
+  "images" : [
+    {
+      "idiom" : "universal",
+      "scale" : "1x"
+    },
+    {
+      "idiom" : "universal",
+      "filename" : "placeholder@2x.png",
+      "scale" : "2x"
+    },
+    {
+      "idiom" : "universal",
+      "filename" : "placeholder@3x.png",
+      "scale" : "3x"
+    }
+  ],
+  "info" : {
+    "version" : 1,
+    "author" : "xcode"
+  }
+}

Passepartout-iOS/Scenes/Organizer/OrganizerViewController.swift

@@ -473,9 +473,14 @@ extension OrganizerViewController {
         case .profile:
             let cell = Cells.setting.dequeue(from: tableView, for: indexPath)
             let rowProfile = profileKey(at: indexPath)
-            if rowProfile.context == .provider, let metadata = InfrastructureFactory.shared.metadata(forName: rowProfile.id) {
-                cell.imageView?.image = metadata.logo
-                cell.leftText = metadata.description
+            if rowProfile.context == .provider {
+                if let metadata = InfrastructureFactory.shared.metadata(forName: rowProfile.id) {
+                    cell.imageView?.image = metadata.logo
+                    cell.leftText = metadata.description
+                } else {
+                    cell.imageView?.image = Asset.Providers.placeholder.image
+                    cell.leftText = rowProfile.id
+                }
             } else {
                 cell.imageView?.image = nil
                 cell.leftText = rowProfile.id