Merge #1268: Fix RemoteBackend::Undefined panic because of skipped step

877b95e52ddb3871f0469253d121a157f028798d Fix RemoteBackend::Undefined panic because of skipped step (edouardparis)

Pull request description:

  Because Testnet and regtest do not ask user the choice of backend the install panic as the RemoteBackend enum stays to undefined

  close #1264

ACKs for top commit:
  edouardparis:
    Self-ACK 877b95e52ddb3871f0469253d121a157f028798d

Tree-SHA512: 80b3ca99e8848bb2025174874307e6931947548c5964c7a6dd46517becb40c7a9fdd5a51385d24167541374ce8219bb6d04d96a20a8b3d8aefcef6a936346025

gui/src/installer/mod.rs

@@ -102,9 +102,14 @@ impl Installer {
         let context = Context::new(
             network,
             destination_path.clone(),
-            remote_backend
-                .map(RemoteBackend::WithoutWallet)
-                .unwrap_or(RemoteBackend::Undefined),
+            remote_backend.map(RemoteBackend::WithoutWallet).unwrap_or(
+                if matches!(network, Network::Bitcoin | Network::Signet) {
+                    RemoteBackend::Undefined
+                } else {
+                    // The step for choosing the backend will be skipped.
+                    RemoteBackend::None
+                },
+            ),
         );
         let mut installer = Installer {
             network,