esp bug 5

ESP had a problem with empty case statements, it would lose the symbolic 'thread' that followed.

module bob ();
reg [31:0] a;

initial begin
        a = 42;

        case (a)
        42:     ;       // This is the bug, this 'thread' disappears
        endcase

        $write("\n\nALL DONE\n\n");     // And we never see this
        $finish;
end
endmodule