unix-ffi/sqlite3: Fix statements not being finalized.

Currently, statements are only finalized upon a call to Cursor.close().
However, in Cursor.execute() new statements get created without the
previous statements being finalized, causing those to get leaked,
preventing the database from being closed. The fix addresses this by
finalizing the previous statement if it exists.

Signed-off-by: Robert Klink <rhermanklink@ripe.net>

unix-ffi/sqlite3/sqlite3.py

@@ -84,6 +84,11 @@ class Cursor:
         self.stmnt = None
 
     def execute(self, sql, params=None):
+        if self.stmnt:
+            # If there is an existing statement, finalize that to free it
+            res = sqlite3_finalize(self.stmnt)
+            check_error(self.h, res)
+
         if params:
             params = [quote(v) for v in params]
             sql = sql % tuple(params)