fix(knowledge): treat empty rerankerInputCount as unset

An empty string from the Documents Sent to Reranker input passed the
undefined/null guard, so Number('') = 0 → clamped to 1, sending only 1
document to the reranker instead of falling back to the 4× topK auto
default. Add the empty-string check to the guard.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: waleedlatif1

apps/sim/tools/knowledge/search.ts

@@ -100,7 +100,9 @@ export const knowledgeSearchTool: ToolConfig<any, KnowledgeSearchResponse> = {
       const rerankerApiKey =
         typeof params.apiKey === 'string' && params.apiKey.length > 0 ? params.apiKey : undefined
       const rawInputCount =
-        params.rerankerInputCount !== undefined && params.rerankerInputCount !== null
+        params.rerankerInputCount !== undefined &&
+        params.rerankerInputCount !== null &&
+        params.rerankerInputCount !== ''
           ? Number(params.rerankerInputCount)
           : Number.NaN
       const rerankerInputCount = Number.isFinite(rawInputCount)