Correct check condition on group field (#493)

backend/ibutsu_server/widgets/filter_heatmap.py

@@ -43,7 +43,7 @@ def _get_heatmap(filters, builds, group_field, project=None):
 
     # generate the group_field
     group_field = string_to_column(group_field, Run)
-    if not group_field:
+    if group_field is None:
         return {}
 
     # get the runs on which to run the aggregation, we select from a subset of runs to improve

backend/ibutsu_server/widgets/jenkins_heatmap.py

@@ -101,7 +101,7 @@ def _get_heatmap(job_name, builds, group_field, count_skips, project=None, addit
 
     # generate the group_fields
     group_field = string_to_column(group_field, Run)
-    if not group_field:
+    if group_field is None:
         return {}, builds
 
     job_name = string_to_column("metadata.jenkins.job_name", Run)

backend/ibutsu_server/widgets/result_aggregator.py

@@ -36,7 +36,7 @@ def _get_recent_result_data(group_field, days, project=None, run_id=None, additi
 
     # generate the group field
     group_field = string_to_column(group_field, Result)
-    if not group_field:
+    if group_field is None:
         return []
 
     # create the query

backend/ibutsu_server/widgets/run_aggregator.py

@@ -26,7 +26,8 @@ def _get_recent_run_data(weeks, group_field, project=None, additional_filters=No
 
     # generate the group field
     group_field = string_to_column(group_field, Run)
-    if not group_field:
+
+    if group_field is None:
         return data
 
     # create the query