RangeError (index): Invalid value: Valid value range is empty: -1

[zhixinUser01]

when tex is \begin{Vmatrix}\end{Vmatrix}, report error, this is writed by user

════════ Exception caught by rendering library ═════════════════════════════════
The following RangeError was thrown during performLayout():
RangeError (index): Invalid value: Valid value range is empty: -1
The relevant error-causing widget was
Math
When the exception was thrown, this was the stack
#229 RenderObject.layout
object.dart:1915
#230 _RenderTheatre.performLayout
overlay.dart:749
#231 RenderObject.layout
object.dart:1915
#232 RenderProxyBoxMixin.performLayout
proxy_box.dart:116
#233 RenderObject.layout
object.dart:1915
#234 RenderProxyBoxMixin.performLayout
proxy_box.dart:116
#235 _RenderCustomClip.performLayout
proxy_box.dart:1376
#236 RenderObject.layout
object.dart:1915
#237 RenderProxyBoxMixin.performLayout
proxy_box.dart:116
#238 RenderObject.layout
object.dart:1915
#239 RenderProxyBoxMixin.performLayout
proxy_box.dart:116
#240 RenderObject.layout
object.dart:1915
#241 RenderProxyBoxMixin.performLayout
proxy_box.dart:116
#242 RenderObject.layout
object.dart:1915
#243 RenderProxyBoxMixin.performLayout
proxy_box.dart:116
#244 RenderObject.layout
object.dart:1915
#245 RenderView.performLayout
view.dart:165
#246 RenderObject._layoutWithoutResize
object.dart:1757
#247 PipelineOwner.flushLayout
object.dart:887
#248 RendererBinding.drawFrame
binding.dart:504
#249 WidgetsBinding.drawFrame
binding.dart:892
#250 RendererBinding._handlePersistentFrameCallback
binding.dart:370
#251 SchedulerBinding._invokeFrameCallback
binding.dart:1146
#252 SchedulerBinding.handleDrawFrame
binding.dart:1083
#253 SchedulerBinding.scheduleWarmUpFrame.
binding.dart:864
(elided 4 frames from class _RawReceivePortImpl, class _Timer, and dart:async-patch)
The following RenderObject was being processed when the exception was fired: RenderCustomLayout#82fa0 relayoutBoundary=up20 NEEDS-LAYOUT NEEDS-PAINT
RenderObject: RenderCustomLayout#82fa0 relayoutBoundary=up20 NEEDS-LAYOUT NEEDS-PAINT
parentData: (can use size)
constraints: BoxConstraints(unconstrained)
size: MISSING

[DamianoMagrini]

Same issue is caused by \begin{pmatrix}\end{pmatrix}, whereas other empty environments, like \begin{cases}\end{cases}, cause no error.

[DamianoMagrini]

Got it, the issue is at lines 332-333 of lib/src/ast/nodes/matrix.dart, i.e.

colPos[cols - 1] = pos;
pos += colWidths[cols - 1];

where index cols - 1 is accessed even if cols is zero. Wrapping the two lines above in an if (cols != 0) conditional solves the issue, but I don't really have a deep understanding of the code and I fear I might be missing something. Should I submit a PR with the described change or are there other lines that should not be executed (or should be executed differently) if the matrix has no columns?