TVMC: Don't divide trials by zero tasks (#10164)

If there are no tasks to tune, the number of trails is meaningless.

Co-authored-by: Martin Kröning <martin.kroening@neclab.eu>

python/tvm/driver/tvmc/autotuner.py

@@ -468,7 +468,7 @@ def tune_model(
 
         # In autotvm, trials is specified per task. We can convert the per-model input
         # provided to per-task trials by dividing by the number of tasks.
-        trials = int(trials / len(tasks))
+        trials = int(trials / max(len(tasks), 1))
         logger.info("Autotuning with %d trials per task.", trials)
 
         tuning_options = {