when iam opening the created wlf file iam getting below message

assertions]% Reading pref.tcl

WLF file vsim.wlf contains no context information.

Hi,

When i am simulating below code iam getting the message above and waveform is not getting opened.

It would be really helpfull if someone helps me to fix this issue.

program main;

  bit [7:0] data;

  bit clk=0,rst;

  property unknown_check;

    @(posedge clk)

      disable iff(rst) $isunknown(data);

  endproperty         

  unknow_property:assert property(unknown_check);

  initial begin

    $display("Entered initial to drive data");         

    rst=1;

    #2;

    data=8'h20;

    #20

    data=8'hX;

  end

  initial

    forever #2 clk=~clk;

  initial begin

    $dumpfile("");

    $wlfdumpvars;

    $dumpon;

  end         

endprogram