gh-111277: In summarize_stats.py, don't fail fast on invalid ratios

Author: mdboom

Tools/scripts/summarize_stats.py

@@ -419,8 +419,6 @@ def __init__(self, num: int, den: int | None, percentage: bool = True):
         self.num = num
         self.den = den
         self.percentage = percentage
-        if den == 0 and num != 0:
-            raise ValueError("Invalid denominator")
 
     def __float__(self):
         if self.den == 0:
@@ -432,6 +430,8 @@ def __float__(self):
 
     def markdown(self) -> str:
         if self.den == 0 or self.den is None:
+            if self.num != 0:
+                return f"{self.num:,} / 0 !!"
             return ""
         elif self.percentage:
             return f"{self.num / self.den:,.01%}"