From bd4aba2572c75c6575df5a63d06dda6c9563af24 Mon Sep 17 00:00:00 2001
From: Ghostkeeper <rubend@tutanota.com>
Date: Tue, 27 Mar 2018 09:28:19 +0200
Subject: [PATCH] Return empty extruder list if no global stack

Just about every call of this function (except 2) would break when this returns None. The signature also says it doesn't return None. Let's return an empty list instead.

Contributes to issue CURA-5045.
---
 cura/Settings/ExtruderManager.py |  2 +-
 cura/Settings/MachineManager.py  | 22 ++++++++++------------
 2 files changed, 11 insertions(+), 13 deletions(-)

diff --git a/cura/Settings/ExtruderManager.py b/cura/Settings/ExtruderManager.py
index 2b422ec406..c2fe929957 100755
--- a/cura/Settings/ExtruderManager.py
+++ b/cura/Settings/ExtruderManager.py
@@ -366,7 +366,7 @@ class ExtruderManager(QObject):
     def getActiveExtruderStacks(self) -> List["ExtruderStack"]:
         global_stack = Application.getInstance().getGlobalContainerStack()
         if not global_stack:
-            return None
+            return []
 
         result = []
         if global_stack.getId() in self._extruder_trains:
diff --git a/cura/Settings/MachineManager.py b/cura/Settings/MachineManager.py
index 6694bba0d6..8695252737 100755
--- a/cura/Settings/MachineManager.py
+++ b/cura/Settings/MachineManager.py
@@ -509,12 +509,11 @@ class MachineManager(QObject):
         result = {}
 
         active_stacks = ExtruderManager.getInstance().getActiveExtruderStacks()
-        if active_stacks is not None:  # If we have extruder stacks
-            for stack in active_stacks:
-                material_container = stack.material
-                if not material_container:
-                    continue
-                result[stack.getId()] = material_container.getId()
+        for stack in active_stacks:
+            material_container = stack.material
+            if not material_container:
+                continue
+            result[stack.getId()] = material_container.getId()
 
         return result
 
@@ -961,12 +960,11 @@ class MachineManager(QObject):
         result = {}
 
         active_stacks = ExtruderManager.getInstance().getActiveExtruderStacks()
-        if active_stacks is not None:
-            for stack in active_stacks:
-                variant_container = stack.variant
-                position = stack.getMetaDataEntry("position")
-                if variant_container and variant_container != self._empty_variant_container:
-                    result[position] = variant_container.getName()
+        for stack in active_stacks:
+            variant_container = stack.variant
+            position = stack.getMetaDataEntry("position")
+            if variant_container and variant_container != self._empty_variant_container:
+                result[position] = variant_container.getName()
 
         return result