fix: handle 'None' baseline values by defaulting to 0.0 in read_baseline

When a baseline file contains "None" as the best time (e.g. when no interpreter
was available during baseline generation), the previous code attempted to parse
it as float and failed. This change checks if the value starts with "None" and
assigns 0.0 instead, allowing benchmarks without a valid baseline to proceed
without crashing.

util/benchmark.py

@@ -288,7 +288,10 @@ def read_baseline():
         name, best = line.split(",")
         for benchmark in BENCHMARKS:
           if benchmark[0] == name:
-            benchmark[2] = float(best)
+            if not best.startswith("None"):
+              benchmark[2] = float(best)
+            else:
+              benchmark[2] = 0.0
 
 
 def generate_baseline():