Remove two pointless assert() statements. This should silence harmless

compiler warnings reported at 
[https://bugzilla.mozilla.org/show_bug.cgi?id=1152845]

FossilOrigin-Name: 83b342a44ffc9ea07dc4d59f2866cefc68ee4f13

src/build.c

@@ -3776,7 +3776,6 @@ void sqlite3SrcListIndexedBy(Parse *pParse, SrcList *p, Token *pIndexedBy){
 void sqlite3SrcListShiftJoinType(SrcList *p){
   if( p ){
     int i;
-    assert( p->a || p->nSrc==0 );
     for(i=p->nSrc-1; i>0; i--){
       p->a[i].jointype = p->a[i-1].jointype;
     }

src/trigger.c

@@ -680,7 +680,6 @@ static SrcList *targetSrcList(
   pSrc = sqlite3SrcListAppend(pParse->db, 0, &pStep->target, 0);
   if( pSrc ){
     assert( pSrc->nSrc>0 );
-    assert( pSrc->a!=0 );
     iDb = sqlite3SchemaToIndex(pParse->db, pStep->pTrig->pSchema);
     if( iDb==0 || iDb>=2 ){
       sqlite3 *db = pParse->db;