HS: Minor fix.

src/Model/HydraulicStructures/HydraulicStructures.py

@@ -118,8 +118,8 @@ class HydraulicStructure(SQLSubModel):
             )
 
             hs.enabled = enabled
-            hs.input_kp = input_kp
-            hs.output_kp = output_kp
+            hs.input_kp = input_kp if input_kp != -1 else None
+            hs.output_kp = output_kp if output_kp != -1 else None
 
             hs.input_reach, hs.output_reach = reduce(
                 lambda acc, n: (