Correctly handle HSplit/VSplit instances without children.

2 files changed, 7 insertions, 0 deletions

diff --git a/prompt_toolkit/layout/containers.py b/prompt_toolkit/layout/containers.py
index 2b0e20d7..035af995 100644
--- a/prompt_toolkit/layout/containers.py
+++ b/prompt_toolkit/layout/containers.py
@@ -157,6 +157,9 @@ class HSplit(Container):
         Return the heights for all rows.
         Or None when there is not enough space.
         """
+        if not self.children:
+            return []
+
         # Calculate heights.
         given_dimensions = self.get_dimensions(cli) if self.get_dimensions else None
 
@@ -260,6 +263,9 @@ class VSplit(Container):
         Return the widths for all columns.
         Or None when there is not enough space.
         """
+        if not self.children:
+            return []
+
         # Calculate widths.
         given_dimensions = self.get_dimensions(cli) if self.get_dimensions else None
 
diff --git a/prompt_toolkit/utils.py b/prompt_toolkit/utils.py
index 0c49bb3f..d2f8606d 100644
--- a/prompt_toolkit/utils.py
+++ b/prompt_toolkit/utils.py
@@ -194,6 +194,7 @@ def take_using_weights(items, weights):
     assert isinstance(weights, list)
     assert all(isinstance(i, int) for i in weights)
     assert len(items) == len(weights)
+    assert len(items) > 0
 
     already_taken = [0 for i in items]
     item_count = len(items)