Fix font settings for button card (#25607)

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

@@ -224,19 +224,19 @@ export class HuiButtonCard extends LitElement implements LovelaceCard {
                   filter: colored ? stateColorBrightness(stateObj) : undefined,
                   height: this._config.icon_height
                     ? this._config.icon_height
-                    : "",
+                    : undefined,
                 })}
               ></ha-state-icon>
             `
-          : ""}
+          : nothing}
         ${this._config.show_name
           ? html`<span tabindex="-1" .title=${name}>${name}</span>`
-          : ""}
+          : nothing}
         ${this._config.show_state && stateObj
           ? html`<span class="state">
               ${this.hass.formatEntityState(stateObj)}
             </span>`
-          : ""}
+          : nothing}
       </ha-card>
     `;
   }
@@ -282,7 +282,8 @@ export class HuiButtonCard extends LitElement implements LovelaceCard {
           align-items: center;
           text-align: center;
           padding: 4% 0;
-          font-size: 16.8px;
+          font-size: var(--ha-font-size-l);
+          line-height: var(--ha-line-height-condensed);
           height: 100%;
           box-sizing: border-box;
           justify-content: center;