added simple if condition to fix the issue of unmatching and front and back endografts

endograft_generation.py

@@ -137,6 +137,9 @@ def estimate_stretch_factor(centerline, arc_lengths, frames, distance, radial_ve
 # Fabric Component
 def create_fabric(centerline, frames, start_position, length, diameter, start_amplitude_pp=2.0, waves=8, phase_angle=0.0):
 
+    if length <= 0:
+        return vtk.vtkPolyData()
+
     arc_lengths = arc_length(centerline)
     phase_rad = np.radians(phase_angle)