Fix an assert() failure caused by setting "PRAGMA journal_mode=off" on an database in exclusive-mode that has already opened the journal file.

FossilOrigin-Name: 40db3e40126db1035fcc12989026915744dc5651

src/pager.c

@@ -7010,6 +7010,8 @@ int sqlite3PagerSetJournalMode(Pager *pPager, int eMode){
         }
         assert( state==pPager->eState );
       }
+    }else if( eMode==PAGER_JOURNALMODE_OFF ){
+      sqlite3OsClose(pPager->jfd);
     }
   }