Fix Inactive Volume for constant volumes

pyradiomics_radler/myfirstorder.py

 import numpy
-from scipy import ndimage
 from oct2py import Oct2Py, Oct2PyError
+from scipy import ndimage
 
 from radiomics.firstorder import RadiomicsFirstOrder
+
 from .mybase import MyRadiomicsFeaturesBase
 
 
@@ -234,12 +235,12 @@ class MyRadiomicsFirstOrder(MyRadiomicsFeaturesBase):
         a threshold of 0.01 × (SUVmax)^2 followed by closing and opening morphological operations were used 
         to differentiate active and inactive regions on FDG-PET scans
         
-        - input: 3D array representing the PET volume in SUV format, with 
-                voxels outside the ROI set to NaNs.
+        - input: 3D array representing the PET volume in SUV format
 
         .. note::
         Extracted from PET scans and not used in the CT feature set.
         """
+
         ROIPet = self.imageArray
         mask = self.maskArray
 
@@ -298,27 +299,31 @@ class MyRadiomicsFirstOrder(MyRadiomicsFeaturesBase):
 
                 connObjects = oc.bwconncomp(new_mask, 26)
 
-                b = numpy.zeros((1, int(connObjects.NumObjects)))
+                if int(connObjects.NumObjects) > 1:
 
-                for i in range(int(connObjects.NumObjects)):
-                    if isinstance(connObjects.PixelIdxList[0][i], numpy.ndarray):
-                        a = connObjects.PixelIdxList[0][i].shape[0]
-                        # If the number of of pixel forming and object is lower than 15, reject it
-                        if a < 15:
-                            b[:, i] = 0
+                    b = numpy.zeros((1, int(connObjects.NumObjects)))
+
+                    for i in range(int(connObjects.NumObjects)):
+                        if isinstance(connObjects.PixelIdxList[0][i], numpy.ndarray):
+                            a = connObjects.PixelIdxList[0][i].shape[0]
+                            # If the number of of pixel forming and object is lower than 15, reject it
+                            if a < 15:
+                                b[:, i] = 0
+                            else:
+                                b[:, i] = 1
                         else:
-                            b[:, i] = 1
-                    else:
-                        b[:, i] = 0
+                            b[:, i] = 0
 
-                rows, cols = numpy.where(b > 0)
-                sumInactive = sum(
-                    [
-                        connObjects.PixelIdxList[rows, cols][i].shape[0]
-                        for i in range(len(cols))
-                    ]
-                )
+                    rows, cols = numpy.where(b > 0)
+                    sumInactive = sum(
+                        [
+                            connObjects.PixelIdxList[rows, cols][i].shape[0]
+                            for i in range(len(cols))
+                        ]
+                    )
 
+                else:
+                    sumInactive = 0
                 sumVolume = numpy.sum(mask)
 
             except Oct2PyError as e: