BC: Fix get_assoc_to_node in case of no results.

src/Model/BoundaryCondition/BoundaryConditionList.py

@@ -91,9 +91,14 @@ class BoundaryConditionList(PamhyrModelListWithTab):
         return copy(self)
 
     def get_assoc_to_node(self, tab, node):
-        return next(
+        assoc = list(
             filter(
                 lambda i: i.node is node,
                 self._tabs[tab]
             )
         )
+
+        if len(assoc) > 0:
+            return assoc[0]
+
+        return None