Fixed Length SQL Query Question

I am working on a Fixed Length Query and need help when the value is NULL. In this section of code below, the Attending Doctors Middle Initial is almost always missing; however, because it is NULL, I still need to pad a space in the column. I need to pad 1 space if null.

SELECT 
			    OP8001_RecordType = '80'
			  , OP8002_Sequence = '01'
			  , OP8003_PatientControlNumber = UPPER(pv.TicketNumber)
			  , OP8097_Filler1 = SPACE(2)
			  , OP8004_AttendingProviderNPI = LEFT(ad.NPI , 16)
			  , OP8098_Filler2 = SPACE(32)
			  , OP8006_AttendingProviderLastName = LEFT(ad.Last , 16)
			  , OP8007_AttendingProviderFirstName = LEFT(ad.First , 8)
			  , OP8008_AttendingProviderMiddleInt = LEFT(ad.Middle , 1) 
			  , OP8099_Filler3 = SPACE(52)
		 FROM #MHDO M
				JOIN PatientVisit pv ON M.PatientVisitId = pv.PatientVisitId
				JOIN DoctorFacility ad ON M.AttendingDoctorId = ad.DoctorFacilityId; 

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