Auto-embeddings not applied on an empty string.

[donhardman]

Bug Description:

MRE:

mysql -h0 -P9306 -e "CREATE TABLE test_knn_select (id BIGINT, title TEXT, content TEXT, category string attribute, embedding FLOAT_VECTOR KNN_TYPE='hnsw' HNSW_SIMILARITY='l2' MODEL_NAME='sentence-transformers/all-MiniLM-L6-v2' FROM='title, content') engine='columnar'"; echo $?
mysql -h0 -P9306 -e "SELECT id, title, knn_dist() FROM test_knn_select WHERE knn(embedding, 2, '')"

Result:

ERROR 1064 (42000) at line 1: table test_knn_select: KNN index 'embedding' requires a vector of 384 entries; 0 entries specified

Manticore Search Version:

Latest dev

Operating System Version:

Ubuntu

Have you tried the latest development version?

None

Internal Checklist:

^{To be completed by the assignee. Check off tasks that have been completed or are not applicable.}

• Implementation completed
• Tests developed
• Documentation updated
• Documentation reviewed