fix: use default idle conn value if none provided

Author: carocad

backend/core/runner/db.go

@@ -60,6 +60,9 @@ func NewGormDbEx(configReader config.ConfigReader, logger log.Logger, sessionCon
 	}
 
 	idleConns := configReader.GetInt("DB_IDLE_CONNS")
+	if idleConns == 0 {
+		idleConns = 10
+	}
 	dbMaxOpenConns := configReader.GetInt("DB_MAX_CONNS")
 	if dbMaxOpenConns <= 0 {
 		dbMaxOpenConns = 100