Don't display slider if light doesn't support brightness (#3684)

Closes https://github.com/home-assistant/home-assistant-polymer/issues/3542

src/panels/lovelace/cards/hui-light-card.ts

@@ -25,6 +25,8 @@ import { LovelaceCard, LovelaceCardEditor } from "../types";
 import { hasConfigOrEntityChanged } from "../common/has-changed";
 import { toggleEntity } from "../common/entity/toggle-entity";
 import { LightCardConfig } from "./types";
+import { supportsFeature } from "../../../common/entity/supports-feature";
+import { SUPPORT_BRIGHTNESS } from "../../../data/light";
 
 @customElement("hui-light-card")
 export class HuiLightCard extends LitElement implements LovelaceCard {
@@ -90,12 +92,17 @@ export class HuiLightCard extends LitElement implements LovelaceCard {
           class="more-info"
           @click="${this._handleMoreInfo}"
         ></paper-icon-button>
+
         <div id="light">
+          ${supportsFeature(stateObj, SUPPORT_BRIGHTNESS)
+            ? html`
                 <round-slider
                   .value=${brightness}
                   @value-changing=${this._dragEvent}
                   @value-changed=${this._setBrightness}
                 ></round-slider>
+              `
+            : ""}
           <ha-icon
             class="light-icon"
             data-state="${stateObj.state}"
@@ -107,6 +114,7 @@ export class HuiLightCard extends LitElement implements LovelaceCard {
             @click="${this._handleTap}"
           ></ha-icon>
         </div>
+
         <div id="tooltip">
           <div class="brightness" @ha-click="${this._handleTap}">
             ${brightness} %