Add a failing assert to check something in the OSS-Fuzz build

Signed-off-by: Gavin D. Howard <[email protected]>

src/vm.c

@@ -1832,6 +1832,8 @@ bc_vm_atexit(BcStatus status)
  // Set the status correctly.
  BcStatus s = BC_STATUS_IS_ERROR(status) ? status : BC_STATUS_SUCCESS;
 
+ assert(false);
+
  bc_vm_shutdown();
 
 #if BC_DEBUG