Lazy load css for legacy themes

Author: KoolADE85

src/lib/components/AgGrid.react.js

@@ -103,11 +103,12 @@ function DashAgGrid(props) {
 
     const shouldLoadLegacyCSS = useMemo(() => {
         // Only load legacy CSS if theme is 'legacy' or unset
+        const dashGridOptions = props.dashGridOptions || {};
         return (
-            !('theme' in props.dashGridOptions) ||
-            props.dashGridOptions.theme === 'legacy'
+            !('theme' in dashGridOptions) ||
+            dashGridOptions.theme === 'legacy'
         );
-    }, [props.dashGridOptions.theme]);
+    }, [props.dashGridOptions]);
 
     const LegacyThemeLoader = useMemo(() => {
         if (