Fix render() override

Author: davet2001

src/dialogs/config-flow/previews/flow-preview-generic.ts

@@ -26,7 +26,7 @@ export class FlowPreviewGeneric extends LitElement {
 
   @state() protected _preview?: HassEntity;
 
-  @state() private _error?: string;
+  @state() protected _error?: string;
 
   private _unsub?: Promise<UnsubscribeFunc>;
 

src/dialogs/config-flow/previews/flow-preview-generic_camera.ts

@@ -1,12 +1,12 @@
-import { html, nothing } from "lit";
+import { html } from "lit";
 import { customElement } from "lit/decorators";
 import { FlowPreviewGeneric } from "./flow-preview-generic";
 
 @customElement("flow-preview-generic_camera")
 class FlowPreviewGenericCamera extends FlowPreviewGeneric {
   protected override render() {
     if (!this._preview) {
-      return nothing;
+      return html`<ha-alert alert-type="error">${this._error}</ha-alert>`;
     }
 
     const stillUrl = this._preview.attributes.stillUrl;