feat(template): do not print new lines if value of flag is None

filter_plugins/docker_filters.py

@@ -1,9 +1,11 @@
 # filter_plugins/docker_filters.py
 
-
 def create_docker_flags(flags):
     if flags:
-        return "\n".join([create_docker_flag(item) for item in flags])
+        filtered_flags = [
+            create_docker_flag(item) for item in flags if create_docker_flag(item)
+        ]
+        return "\n".join(filtered_flags)
     return None
 
 
@@ -11,14 +13,16 @@ def create_docker_flag(item):
     if isinstance(item, dict):
         key = list(item.keys())[0]
         value = item[key]
+        if value is not None:
             if isinstance(value, list):
-            return "\n".join(['--{} "{}" \\'.format(key, val) for val in value])
+                flag_values = ['--{} "{}"'.format(key, val) for val in value]
+                joined_values = " \\\n".join(flag_values)
+                return f"{joined_values} \\" if joined_values else None
             else:
                 return '--{} "{}" \\'.format(key, value)
     elif isinstance(item, str):
         return "--{} \\".format(item)
-    else:
+    return None
-        return ""
 
 
 class FilterModule(object):