feat(tool): fix failing tests

Author: JigyasuRajput

cve_bin_tool/vex_manager/validate.py

@@ -194,7 +194,9 @@ def validate_file(
             # Use traditional jsonschema validation for CSAF and OpenVEX
             try:
                 schema = self._get_schema(vex_type, version)
-                if schema:  # Only validate if schema was successfully loaded
+                if (
+                    schema and len(schema) > 0
+                ):  # Only validate if schema was successfully loaded and not empty
                     jsonschema.validate(instance=raw_data, schema=schema)
                     self.logger.info(f"VEX file passed {vex_type} schema validation")
             except JsonSchemaValidationError as e: