Set data list to [0] if list is empty

Empty list values are causing issues with perf JSON data upload. Hence,
setting list to [0] if it is empty.

BUG=chromium:739544
TEST=Tested on a local setup

Change-Id: I27c2e40f4286cda6b3e1ccbae921b8f21a6d015a
Reviewed-on: https://chromium-review.googlesource.com/572303
Reviewed-by: Kalin Stoyanov <kalin@chromium.org>
Reviewed-by: Harpreet Grewal <harpreet@chromium.org>
Commit-Queue: Harpreet Grewal <harpreet@chromium.org>
Tested-by: Harpreet Grewal <harpreet@chromium.org>
Trybot-Ready: Harpreet Grewal <harpreet@chromium.org>
diff --git a/server/cros/cfm_jmidata_v3_helper.py b/server/cros/cfm_jmidata_v3_helper.py
index ec33c42..bd32859 100644
--- a/server/cros/cfm_jmidata_v3_helper.py
+++ b/server/cros/cfm_jmidata_v3_helper.py
@@ -218,6 +218,8 @@
                     elif (cpu_type in global_obj and
                             self.IsFloat(global_obj[cpu_type])):
                         data_list.append(float(global_obj[cpu_type]))
+        if not data_list:
+            data_list = [0]
         return data_list
 
     def GetNumOfProcessors(self):