Add new assert() statements in an attempt to help static analyzers avoid

false-positives.

FossilOrigin-Name: 9e66458592d40fbd96ea5f21339573110ca1cfe328238a020c9420a87d35dd72

src/parse.y

@@ -458,6 +458,7 @@ cmd ::= select(X).  {
   ** SQLITE_LIMIT_COMPOUND_SELECT.
   */
   static void parserDoubleLinkSelect(Parse *pParse, Select *p){
+    assert( p!=0 );
     if( p->pPrior ){
       Select *pNext = 0, *pLoop;
       int mxSelect, cnt = 0;