patch praktika crash when there are no artifacts

Author: strtgbb

ci/praktika/runtime.py

@@ -24,6 +24,8 @@ class RunConfig(MetaClasses.Serializable):
 
     @classmethod
     def from_dict(cls, obj):
+        if obj is None:
+            return obj
         cache_artifacts = obj["cache_artifacts"]
         cache_jobs = obj["cache_jobs"]
         cache_artifacts_deserialized = {}