Add Fallback Logic for Missing Vector Embeddings

[HelloShibani]

Problem

In some cases, document chunks may fail to generate vector embeddings (e.g., due to special characters or model errors).

Proposed Solution

Implement a fallback path:

• Skip problematic chunks
• Log skipped entries
• Optionally default to keyword-based retrieval (e.g., BM25 or text match)

Why it matters

Adds robustness for real-world data ingestion and improves model resilience across document formats.