#984 segfault in vvp processing events with fst dumper

[Larry Doolittle]

The attached fault1 tarball is part of the yosys regression test suite.
When run with IVERILOG_DUMPER=fst, it crashes vvp:

IVERILOG_DUMPER=fst vvp -n code_verilog_tutorial_counter_tb_syn0

FST info: dumpfile counter.vcd opened for output.
Applying reset
Came out of Reset
Terminating simulation
Simulation Result : PASSED

Segmentation fault

To reproduce, unpack the tarball and type "make".
Patch will follow (I don't see how to add two attachments).

[Larry Doolittle]

In private email, Tony Bybell supplied the attached patch, that is tested to fix the crash. His email also asserts "Once fixed, you'll get your impulse arrows in gtkwave as you'd expect" for events in the simulation that should have been there all along.

[Cary R.]

I have applied the patch to both development and V0.9. I will push a test program later.