Have the rtree module close any open blob-handle within the xSavepoint method.

This prevents such an open blob handle from interfering with DROP TABLE
operations.

FossilOrigin-Name: fa4416adc2a9a3a80db1d5befc0b95c3d0fc41affe38f7f2f45cdfae3f1b49eb

ext/rtree/rtree1.test

@@ -39,6 +39,8 @@ set testprefix rtree1
 #               inserted. Also that if a non-numeric is inserted into one
 #               of the min/max dimension columns, it is converted to the
 #               required type before being inserted.
+#   rtree-15.*: Check that DROP TABLE works within a transaction that
+#               writes to an r-tree table.
 #
 
 ifcapable !rtree {
@@ -592,4 +594,20 @@ do_execsql_test 14.5 {
   3 42 49
 }
 
+#-------------------------------------------------------------------------
+#
+do_execsql_test 15.0 {
+  CREATE VIRTUAL TABLE rt USING rtree(id, x1,x2, y1,y2);
+  CREATE TEMP TABLE t13(a, b, c);
+}
+do_execsql_test 15.1 {
+  BEGIN;
+  INSERT INTO rt VALUES(1,2,3,4,5);
+}
+breakpoint
+do_execsql_test 15.2 {
+  DROP TABLE t13;
+  COMMIT;
+}
+
 finish_test