[qu2cu] No need to add 0 to forced set
diff --git a/Lib/fontTools/qu2cu/qu2cu.py b/Lib/fontTools/qu2cu/qu2cu.py
index 008e01d..141b00b 100644
--- a/Lib/fontTools/qu2cu/qu2cu.py
+++ b/Lib/fontTools/qu2cu/qu2cu.py
@@ -287,7 +287,7 @@
     ]
 
     # Find sharp corners; they have to be oncurves for sure.
-    forced = {0}
+    forced = set()
     for i in range(1, len(elevated_quadratics)):
         p0 = elevated_quadratics[i - 1][2]
         p1 = elevated_quadratics[i][0]