TextPanel: Fixed issue with new react text panel (#26061)

(cherry picked from commit 8be735a6ec)

public/app/plugins/panel/text/TextPanel.tsx

@@ -6,6 +6,8 @@ import { PanelProps, renderMarkdown, textUtil } from '@grafana/data';
 import config from 'app/core/config';
 // Types
 import { TextOptions } from './types';
+import { stylesFactory } from '@grafana/ui';
+import { css, cx } from 'emotion';
 
 interface Props extends PanelProps<TextOptions> {}
 interface State {
@@ -75,7 +77,16 @@ export class TextPanel extends PureComponent<Props, State> {
 
   render() {
     const { html } = this.state;
+    const styles = getStyles();
 
-    return <div className="markdown-html panel-text-content" dangerouslySetInnerHTML={{ __html: html }} />;
+    return <div className={cx('markdown-html', styles.content)} dangerouslySetInnerHTML={{ __html: html }} />;
   }
 }
+
+const getStyles = stylesFactory(() => {
+  return {
+    content: css`
+      height: 100%;
+    `,
+  };
+});