ReachTargetVoltage: Fix initial response check

We want to only act specially on the very first sweep. But as we reset the
index, we will land in this branch on every sweep if the resistance is too
small.

Let's prefer comparing to the number of acquired sweeps instead.

Packages/MIES/MIES_AnalysisFunctions.ipf

@@ -1143,8 +1143,10 @@ Function ReachTargetVoltage(string device, STRUCT AnalysisFunction_V3 &s)
 					continue
 				endif
 
+				WAVE sweeps = AFH_GetSweepsFromSameSCI(numericalValues, s.sweepNo, i)
+
 				// check initial response
-				if(index == 0 && resistanceFitted[i] <= 20e6)
+				if(DimSize(sweeps, ROWS) == 1 && resistanceFitted[i] <= 20e6)
 					amps                   = -100e-12
 					targetVoltagesIndex[i] = -1
 				else