software/rapid-cdn: Protect more against unusal values

This part is unit tested against slapproxy, but unfortunately other
implementations of SlapOS Master might return None in such case failing
fully the profile.

Fix it without test, but with marking the problem.

software/rapid-cdn/buildout.hash.cfg

@@ -26,7 +26,7 @@ md5sum = 4a53b09ba4cbf15e32a5088cc81db5ea
 
 [profile-master]
 filename = instance-master.cfg.in
-md5sum = 78c556911944339f0c03c8416db8dbaa
+md5sum = fcc78c9f240974dff2ed5055a2675603
 
 [profile-slave-list]
 filename = instance-slave-list.cfg.in

software/rapid-cdn/instance-master.cfg.in

@@ -316,7 +316,9 @@ context =
 {%-   endfor %}
 {%-   for k in ['ssl_proxy_ca_crt', 'health-check-failover-ssl-proxy-ca-crt'] %}
 {%-     if k in slave %}
-{%-       set crt = slave.get(k, '') %}
+{#-       Be very cautious -- some master implementations are returning None for empty strings #}
+{#-       Thus get can return None so convert it to a string #}
+{%-       set crt = slave.get(k, '') or '' %}
 {%-       set check_popen = popen([software_parameter_dict['openssl'], 'x509', '-noout']) %}
 {%-       do check_popen.communicate(crt.encode()) %}
 {%-       if check_popen.returncode != 0 %}