In sqlite3GenerateIndexKey(), do not attempt to reuse column values from

the previous index if the current index is a partial index as the partial
index test may have corrupted those values.  Ticket [a9efb42811fa41ee]

FossilOrigin-Name: 17e9f65814264de9c35bc5ba94e0a66fbbf1200c00d33ab9a19a0b6f92bc685a

src/delete.c

@@ -918,6 +918,8 @@ int sqlite3GenerateIndexKey(
       sqlite3ExprIfFalseDup(pParse, pIdx->pPartIdxWhere, *piPartIdxLabel, 
                             SQLITE_JUMPIFNULL);
       pParse->iSelfTab = 0;
+      pPrior = 0; /* Ticket a9efb42811fa41ee 2019-11-02;
+                  ** pPartIdxWhere may have corrupted regPrior registers */
     }else{
       *piPartIdxLabel = 0;
     }