PLEASE HELP: ISERROR, ISBLANK with LOOKUP

I am having trouble trying to get ISERROR and ISBLANK to work together in one formula while using LOOKUP with times for a coaching scale. I have some months of data that have not populated, so until I have data collected for those months, I want those cells to remain empty in my Pending Times Score section. I am using the ISERROR formula because I have people who have times lower than 10:00:00, but I get an #N/A unless I use the first formula below. Attached is my sample worksheet.

This formula gives me that I want when I have data in the Pending Times section of my worksheet, but will give all 4's for months when I have no data.
=IF(ISERROR(LOOKUP(B3,Pending_Scale)),4,LOOKUP(B3,Pending_Scale))

This formula will work for the cells that have no data, but will give me a blank when the individual should be getting a score of 4.00

=IF(ISERROR(LOOKUP(H3,PendingScale)),IF(ISBLANK(LOOKUP(H3,PendingScale)),4,""),LOOKUP(H3,PendingScale))