command/meta_backend: Allow the remote backend to have no workspaces [again]

A regression introduced in d72a413ef8

The comment explains, but TLDR: The remote backend actually *depended*
on being able to write it's backend state even though an 'error'
occurred (no workspaces).

internal/command/meta_backend.go

@@ -1025,13 +1025,26 @@ func (m *Meta) backend_C_r_s(c *configs.Backend, cHash int, sMgr *clistate.Local
 		Hash:      uint64(cHash),
 	}
 
-	// Verify that selected workspace exist. Otherwise prompt user to create one
+	// Verify that selected workspace exists in the backend.
 	if opts.Init && b != nil {
-		if err := m.selectWorkspace(b); err != nil {
+		err := m.selectWorkspace(b)
+		if err != nil {
 			diags = diags.Append(err)
+
+			// FIXME: A compatibility oddity with the 'remote' backend.
+			// As an awkward legacy UX, when the remote backend is configured and there
+			// are no workspaces, the output to the user saying that there are none and
+			// the user should create one with 'workspace new' takes the form of an
+			// error message - even though it's happy path, expected behavior.
+			//
+			// Therefore, only return nil with errored diags for everything else, and
+			// allow the remote backend to continue and write its configuration to state
+			// even though no workspace is selected.
+			if c.Type != "remote" {
 				return nil, diags
 			}
 		}
+	}
 
 	if err := sMgr.WriteState(s); err != nil {
 		diags = diags.Append(fmt.Errorf(errBackendWriteSaved, err))