Rig sqlite3_serialize() so that it will initialize a previously uninitialized

database prior to serializing it, so that it does not have a zero-byte size
and does not return NULL (except for OOM).
[forum:/forumpost/498777780e16880a|Forum thread 498777780e16880a].

FossilOrigin-Name: e638d5e408ea2e189b6771d16bbc2e42c606e88e05fbea78079b6e39e41f344c

test/memdb1.test

@@ -267,4 +267,16 @@ if {[wal_is_capable]} {
   } {1 {database disk image is malformed}}
 }
 
+# 2024-01-20
+# https://sqlite.org/forum/forumpost/498777780e16880a
+#
+# Make sure a database is initialized before serializing it.
+#
+reset_db
+sqlite3 dbempty :memory:
+do_test 900 {
+  set len [string length [dbempty serialize]]
+  expr {$len>0}
+} 1
+
 finish_test