code review followup for compress command (#1097)

Followup to https://github.com/google-gemini/gemini-cli/pull/986

packages/cli/src/ui/hooks/useGeminiStream.ts

@@ -379,7 +379,8 @@ export const useGeminiStream = (
           text:
             `IMPORTANT: This conversation approached the input token limit for ${config.getModel()}. ` +
             `A compressed context will be sent for future messages (compressed from: ` +
-            `${eventValue.originalTokenCount} to ${eventValue.newTokenCount} tokens).`,
+            `${eventValue?.originalTokenCount ?? 'unknown'} to ` +
+            `${eventValue?.newTokenCount ?? 'unknown'} tokens).`,
         },
         Date.now(),
       ),