a better fix for the tr_rand() crash experienced earlier today

libtransmission/peer.c

@@ -685,7 +685,7 @@ writeEnd:
                all peers for 2, and so on.  Randomize our starting point
                into "pool" to reduce such overlap */
             int piecesLeft = poolSize;
-            int p = (int)(tr_date() % poolSize);
+            int p = piecesLeft ? tr_rand(piecesLeft) : 0;
             for( ; openSlots>0 && piecesLeft>0; --piecesLeft, p=(p+1)%poolSize )
             {
                 const int piece = pool[p]; 

libtransmission/utils.c

@@ -168,6 +168,9 @@ void tr_msg( int level, char * msg, ... )
 int tr_rand( int sup )
 {
     static int init = 0;
+
+    assert( sup > 0 );
+
     if( !init )
     {
         srand( tr_date() );