Merge pull request #7685 from drew2a/fix/7601

Handle an absent `db_version` for Upgrader.

src/tribler/core/upgrade/db8_to_db10.py

@@ -245,5 +245,8 @@ def get_db_version(db_path):
     with contextlib.closing(sqlite3.connect(db_path)) as connection, connection:
         cursor = connection.cursor()
         cursor.execute('SELECT value FROM MiscData WHERE name == "db_version"')
-        version = int(cursor.fetchone()[0])
+        query_results = cursor.fetchone()
+        if not query_results:
+            return 0
+        version = int(query_results[0])
     return version

src/tribler/core/upgrade/tests/test_db8_to_db10.py

@@ -0,0 +1,11 @@
+from unittest.mock import MagicMock, Mock, patch
+
+from tribler.core.upgrade.db8_to_db10 import get_db_version
+from tribler.core.utilities.path_util import Path
+
+
+def test_get_db_version_no_db_version():
+    """ Test that get_db_version returns 0 if the database version is not found."""
+    cursor = Mock(return_value=Mock(fetchone=Mock(return_value=None)))
+    with patch('tribler.core.upgrade.db8_to_db10.sqlite3.connect', return_value=MagicMock(cursor=cursor)):
+        assert get_db_version(Path()) == 0