Fix no result

app.py

@@ -94,6 +94,8 @@ def _merge_intervals(intervals: list[tuple[float, float]], gap: float = 0.05) ->
     if not intervals:
         return []
     ordered = sorted((float(a), float(b)) for a, b in intervals if b > a)
+    if not ordered:
+        return []
     merged = [ordered[0]]
     for start, end in ordered[1:]:
         prev_start, prev_end = merged[-1]