[openvswitch] catch cases when 'ovs-vsctl list bridge' has no output

If ovs_list_bridge_cmd does not return a valuable output, br_protos
variable won't be assigned before we reference it.

Fix that by assigning an empty list to br_protos .

Resolves: #2249

Signed-off-by: Pavel Moravec <pmoravec@redhat.com>
Signed-off-by: Jake Hunsaker <jhunsake@redhat.com>

sos/report/plugins/openvswitch.py

@@ -219,6 +219,7 @@ def setup(self):
                 ovs_list_bridge_cmd = "ovs-vsctl -t 5 list bridge %s" % br
                 br_info = self.collect_cmd_output(ovs_list_bridge_cmd)
 
+                br_protos = []
                 for line in br_info['output'].splitlines():
                     if "protocols" in line:
                         br_protos_ln = line[line.find("[")+1:line.find("]")]