Visualizer UI subtract with underflow

[janie177]

When using the visualizer's UI to look at multiple memory blocks, a condition can be met where closing one of the windows causes the program to panic.

Error message:

'attempt to subtract with overflow'

The line where it panics:

gpu-allocator-0.21.0\src\vulkan\visualizer.rs:256

[MarijnS95]

gpu-allocator/src/vulkan/visualizer.rs

Line 256 in b92f7cc

if windows_to_close.iter().any(|j| i == (*j - windows_removed)) {