Also show the "unsupported" warning when a custom profile is selected

...by making sure we're looking at the quality container (not quality_changes) of the active extruder/stack

CURA-2271

cura/Settings/MachineManager.py

@@ -492,6 +492,21 @@ class MachineManager(QObject):
                 return quality.getMetaDataEntry("quality_type")
         return ""
 
+    ##  Get the Quality ID associated with the currently active extruder
+    #   Note that this only returns the "quality", not the "quality_changes"
+    #   \returns QualityID (string) if found, empty string otherwise
+    #   \sa activeQualityId()
+    #   \todo Ideally, this method would be named activeQualityId(), and the other one
+    #         would be named something like activeQualityOrQualityChanges() for consistency
+    @pyqtProperty(str, notify = activeQualityChanged)
+    def activeQualityContainerId(self):
+        # We're using the active stack instead of the global stack in case the list of qualities differs per extruder
+        if self._active_container_stack:
+            quality = self._active_container_stack.findContainer(type = "quality")
+            if quality:
+                return quality.getId()
+        return ""
+
     @pyqtProperty(str, notify = activeQualityChanged)
     def activeQualityChangesId(self):
         if self._global_container_stack:

resources/qml/SidebarHeader.qml

@@ -244,7 +244,7 @@ Column
                     }
 
                 }
-                property var valueWarning: Cura.MachineManager.activeQualityId == "empty_quality"
+                property var valueWarning: Cura.MachineManager.activeQualityContainerId == "empty_quality"
 
                 enabled: !extrudersList.visible || base.currentExtruderIndex  > -1