Make it so that any Parse object is always linked into the database conenction

while it is active.  Hence, an OOM will cause Parse.nErr to be set.

FossilOrigin-Name: 6a45d8fe8bfbc11a5b86d25237e1f8bccfb0f22f3dcaf004ba797aeb57b365ec

src/util.c

@@ -189,6 +189,8 @@ void sqlite3ErrorMsg(Parse *pParse, const char *zFormat, ...){
   char *zMsg;
   va_list ap;
   sqlite3 *db = pParse->db;
+  assert( db!=0 );
+  assert( db->pParse==pParse );
   db->errByteOffset = -2;
   va_start(ap, zFormat);
   zMsg = sqlite3VMPrintf(db, zFormat, ap);