Check if SammpleType is set (#2053)

This fixes #2052

Author: ramonski

bika/lims/content/sample.py

@@ -469,9 +469,10 @@
             visible=False,
         ),
     ),
-    ComputedField('SampleTypeUID',
-        expression = 'context.getSampleType().UID()',
-        widget = ComputedWidget(
+    ComputedField(
+        'SampleTypeUID',
+        expression='context.getSampleType() and context.getSampleType().UID() or None',
+        widget=ComputedWidget(
             visible=False,
         ),
     ),

docs/CHANGELOG.txt

@@ -1,7 +1,7 @@
 3.2.1b3 (unreleased)
 --------------------
 
-- no changes yet
+- Issue-2052: Computed Sample Field "SampleTypeUID" does not check if a SampleType is set
 
 
 3.2.1b2 (2017-05-27)