Columns -> Borders demo asserts when columns < 2

[dbechrd]

Dear ImGui 1.72 WIP (17101)
--------------------------------
sizeof(size_t): 4, sizeof(ImDrawIdx): 2, sizeof(ImDrawVert): 20
define: __cplusplus=199711
define: _WIN32
define: _MSC_VER=1921
--------------------------------
io.BackendPlatformName: imgui_impl_glfw
io.BackendRendererName: imgui_impl_opengl3
io.ConfigFlags: 0x00000000
io.ConfigInputTextCursorBlink
io.ConfigWindowsResizeFromEdges
io.BackendFlags: 0x0000000E
 HasMouseCursors
 HasSetMousePos
 RendererHasVtxOffset
--------------------------------
io.Fonts: 1 fonts, Flags: 0x00000000, TexSize: 512,64
io.DisplaySize: 1280.00,720.00
io.DisplayFramebufferScale: 1.00,1.00
--------------------------------
style.WindowPadding: 8.00,8.00
style.WindowBorderSize: 1.00
style.FramePadding: 4.00,3.00
style.FrameRounding: 0.00
style.FrameBorderSize: 0.00
style.ItemSpacing: 8.00,4.00
style.ItemInnerSpacing: 4.00,4.00

Version/Branch of Dear ImGui:

Branch: master@b443bc0a64d5e22d445d2c9cb52f7f39da6b98c9

Back-end/Renderer/Compiler/OS

Affects all back-ends as far as I'm aware.

My Issue/Question:

ShowDemoWindowColumns() triggers assert in imgui_widgets.cpp:

Assertion failed: columns != 0, file imgui\imgui_widgets.cpp, line 7183

Call stack:
example_glfw_opengl3.exe!ImGui::GetColumnWidth(int column_index) Line 7183
example_glfw_opengl3.exe!ShowDemoWindowColumns() Line 2607
example_glfw_opengl3.exe!ImGui::ShowDemoWindow(bool * p_open) Line 408
example_glfw_opengl3.exe!main(int __formal, char * * __formal) Line 137

Screenshots/Video

Standalone, minimal, complete and verifiable example:

Run any of the demo apps on latest master. b443bc0 as of writing.

Drag the 4 columns control (see screenshot) left with mouse, beyond 2 columns. 2 columns works fine, but as soon as you go beyond the app crashes with the assert mentioned above.

[ocornut]

Thank you @dbechrd, fixed this now. It was a mistake that a made that drag reach 1 (I used it while testing the internal BeginColumn api). I took the occasion to actually fix GetColumnWidth and GetColumnOffset to behave kindly when there's no columns active, making them consistent with the other functions.