fix scale_trimMean when outlierLength = 1 #4
Description
In source file ProtFeat.py, line 797, when the sequence is small enough for outlierLength to be equal to 1, scale_trimMean is set as an empty array, rather than the whole array. When the mean of scale_trimMean is then taken at line 818, it throws the warning "RuntimeWarning: Mean of empty slice".