Fix zero height buckets

If max_size is too large relative to max_reso, it will calculate a height of zero for some buckets.
This causes a crash later when it divides the width by the height.

This change also simplifies some math and consolidates the redundant "size" variable into "width".

library/model_util.py

@@ -1307,17 +1307,17 @@ def load_vae(vae_id, dtype):
 
 def make_bucket_resolutions(max_reso, min_size=256, max_size=1024, divisible=64):
     max_width, max_height = max_reso
-    max_area = (max_width // divisible) * (max_height // divisible)
+    max_area = max_width * max_height
 
     resos = set()
 
-    size = int(math.sqrt(max_area)) * divisible
-    resos.add((size, size))
+    width = int(math.sqrt(max_area) // divisible) * divisible
+    resos.add((width, width))
 
-    size = min_size
-    while size <= max_size:
-        width = size
-        height = min(max_size, (max_area // (width // divisible)) * divisible)
+    width = min_size
+    while width <= max_size:
+        height = min(max_size, int((max_area // width) // divisible) * divisible)
+        if height > 0:
             resos.add((width, height))
             resos.add((height, width))
 
@@ -1329,7 +1329,7 @@ def make_bucket_resolutions(max_reso, min_size=256, max_size=1024, divisible=64)
         #   resos.add((width, height - divisible))
         #   resos.add((height - divisible, width))
 
-        size += divisible
+        width += divisible
 
     resos = list(resos)
     resos.sort()