[Malpedia] Fix default_marking recovery error and update readme (Open…

…CTI-Platform#2499)

external-import/malpedia/README.md

@@ -73,5 +73,8 @@ If you are authenticated, then all entities created by the connector will be in
 
 If you are not authenticated, by leaving this variable (auth_key) undefined or only public in the form of an empty string (""), all entities created by the connector will be in TLP:WHITE. This connector can therefore be used without an account.
 
+However, it is possible to use "default_marking" as an environment variable to customize your default marking.
+Markings availables : "TLP:CLEAR", ""TLP:GREEN", "TLP:AMBER", "TLP:RED".
+
 If you choose to set environment variables such as import_intrusion_sets, import_yara, create_indicators, create_observables to false, the connector will simply skip the bundle creation steps for the selected category.
 

external-import/malpedia/src/malpedia_connector/malpedia.py

@@ -45,7 +45,7 @@ def __init__(self) -> None:
             "TLP:AMBER": stix2.TLP_AMBER,
             "TLP:RED": stix2.TLP_RED,
         }
-        self.default_marking = self.config.load["malpedia"].get("default_marking", None)
+        self.default_marking = getattr(self.config, "default_marking", None)
 
         if self.default_marking is not None:
             default_marking_normalized = self.default_marking.strip().upper()