fix: remove empty lines that cause InvalidRequestError (#5320)

# remove empty lines in GenerativeAgentMemory that cause
InvalidRequestError in OpenAIEmbeddings

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Let's say the text given to `GenerativeAgent._parse_list` is
```
text = """
Insight 1: <insight 1>

Insight 2: <insight 2>
"""
```
This creates an `openai.error.InvalidRequestError: [''] is not valid
under any of the given schemas - 'input'` because
`GenerativeAgent.add_memory()` tries to add an empty string to the
vectorstore.

This PR fixes the issue by removing the empty line between `Insight 1`
and `Insight 2`

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langchain/experimental/generative_agents/memory.py

@@ -34,7 +34,7 @@ class GenerativeAgentMemory(BaseMemory):
 
     aggregate_importance: float = 0.0  # : :meta private:
     """Track the sum of the 'importance' of recent memories.
-    
+
     Triggers reflection when it reaches reflection_threshold."""
 
     max_tokens_limit: int = 1200  # : :meta private:
@@ -56,6 +56,7 @@ class GenerativeAgentMemory(BaseMemory):
     def _parse_list(text: str) -> List[str]:
         """Parse a newline-separated string into a list of strings."""
         lines = re.split(r"\n", text.strip())
+        lines = [line for line in lines if line.strip()]  # remove empty lines
         return [re.sub(r"^\s*\d+\.\s*", "", line).strip() for line in lines]
 
     def _get_topics_of_reflection(self, last_k: int = 50) -> List[str]: