Fix bug in SSVC tree pipeline

Signed-off-by: Tushar Goel <tushar.goel.dav@gmail.com>

Author: TG1999

vulnerabilities/pipelines/v2_improvers/collect_ssvc_trees.py

@@ -91,6 +91,9 @@ def collect_ssvc_data(self):
                 try:
                     ssvc_tree, decision = convert_vector_to_tree_and_decision(ssvc_vector)
 
+                    if not (ssvc_tree and decision):
+                        continue
+
                     existing = existing_ssvc.get(advisory.id)
 
                     if existing: