fix: LocalArchivalMemory prints ref_doc_info on if not using EmptyIndex

Currently, if you run the /memory command the application breaks if the LocalArchivalMemory
has no existing archival storage and defaults to the EmptyIndex. This is caused by EmptyIndex
not having a ref_doc_info implementation and throwing an Exception when that is used to print
the memory information to the console. This hot fix simply makes sure that we do not try to
use the function if using EmptyIndex and instead prints a message to the console indicating
an EmptyIndex is used.

memgpt/memory.py

@@ -736,5 +736,8 @@ async def a_search(self, query_string, count=None, start=None):
         return self.search(query_string, count, start)
 
     def __repr__(self) -> str:
-        print(self.index.ref_doc_info)
-        return ""
+        if isinstance(self.index, EmptyIndex):
+            memory_str = "<empty>"
+        else:
+            memory_str = self.index.ref_doc_info
+        return f"\n### ARCHIVAL MEMORY ###" + f"\n{memory_str}"