fix(protocol-designer): pipette channel change patch does not rely on… (

#15676)

… labware

closes RQA-2861

This is a bug in production currently and has been in production since
8.1.0. We decided that its big enough to warrant a fix in the hot fix.
Basically, you can't switch pipettes in a mix step if its between a
single vs 8 channel.

protocol-designer/src/steplist/formLevel/handleFormChange/dependentFieldsUpdateMix.ts

@@ -113,13 +113,16 @@ const updatePatchOnPipetteChannelChange = (
     }
     // multi-channel to single-channel: convert primary wells to all wells
     const labwareId = appliedPatch.labware
-    const labwareDef = labwareEntities[labwareId].def
-    update = {
-      wells: getAllWellsFromPrimaryWells(
-        appliedPatch.wells,
-        labwareDef,
-        channels
-      ),
+
+    if (labwareId != null) {
+      const labwareDef = labwareEntities[labwareId].def
+      update = {
+        wells: getAllWellsFromPrimaryWells(
+          appliedPatch.wells,
+          labwareDef,
+          channels
+        ),
+      }
     }
   }