Bug 511437

Labplot crashes instantly with a `Segmentation fault` when attempting to change a plot's axis scale from "Linear" to "Log10" or any other value. The crash occurs immediately upon clicking the new scale type in the dropdown menu.

1. Application and System Details

  * Application: Labplot
  * Version: 2.12.0 (from crash log)
  * Operating System: macOS 14.2.1 (23C71)
  * Architecture: ARM-64 (Apple Silicon)

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2. Steps to Reproduce

1.  Launch Labplot on macOS.
2.  Create a new spreadsheet.
3.  Copy a column of X-values from an external source (e.g., Excel) and paste them into a spreadsheet column.
4.  Copy a column of Y-values and paste them into another spreadsheet column.
5.  Create a plot from these two columns.
6.  Go to the plot's properties/settings area.
7.  Locate the X-axis or Y-axis scale settings.
8.  Untick the "Auto" setting for the scale.
9.  Click the dropdown menu that currently shows "Linear".
10. Click on any other scale option (e.g., "Log10").

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 3. Expected Behavior

The plot's axis scale should change to the newly selected option (e.g., Log10), and the plot should update.

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 4. Actual Behavior

The Labplot application crashes instantly and closes. This behavior is 100% reproducible.

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 5. Crash Details and Backtrace

The crash is an `EXC_BAD_ACCESS (SIGSEGV)` due to a `KERN_INVALID_ADDRESS at 0x0000000000000008`. This suggests the code is trying to access data from a null pointer (specifically, at an offset of 8 bytes from address 0).

The crash happens in the main thread while processing events related to the `QComboBox` (the dropdown menu).

Backtrace (Thread 0 Crashed)

```
Thread 0 Crashed::  Dispatch queue: com.apple.main-thread
0   QtWidgets                       0x104102f40 0x103e74000 + 2682688
1   libqcocoa.dylib                 0x100cfdffc 0x100c7c000 + 532476
2   AppKit                          0x1855454f8 __NSAccessibilityEntryPointIsAccessibilityElement_block_invoke + 424
3   AppKit                          0x18554530c NSAccessibilityPerformEntryPointBOOL + 44
4   AppKit                          0x184f5b63c NSAccessibilityEntryPointIsAccessibilityElement + 140
5   AppKit                          0x18504c9dc NSAccessibilityUnignoredAncestor + 24
6   AppKit                          0x1859950b0 -[NSWindow(NSWindowAccessibility) accessibilityFocusedUIElement] + 88
7   AppKit                          0x184fb0770 NSAccessibilityHandleFocusChangedForce + 136
8   AppKit                          0x184fcfcc8 -[NSWindow _realMakeFirstResponder:] + 724
9   libqcocoa.dylib                 0x100cbc370 0x100c7c000 + 263024
10  libqcocoa.dylib                 0x100cbc5f4 0x100c7c000 + 263668
11  QtGui                           0x104bcfe08 QWindowPrivate::destroy() + 196
12  QtWidgets                       0x103eeb860 0x103e74000 + 489568
13  QtWidgets                       0x103eeb980 0x103e74000 + 489856
14  QtWidgets                       0x103ec3a1c QWidget::destroy(bool, bool) + 664
15  QtWidgets                       0x103ec307c QWidget::~QWidget() + 1172
16  QtWidgets                       0x103fa59ac QComboBoxPrivateContainer::~QComboBoxPrivateContainer() + 140
17  QtWidgets                       0x103fa8ddc QComboBox::~QComboBox() + 140
18  labplot                         0x10017ebc4 0x100004000 + 1551300
19  QtCore                          0x10454b190 QObject::event(QEvent*) + 696
20  QtWidgets                       0x103ed5d3c QWidget::event(QEvent*) + 3236
21  QtWidgets                       0x103fad35c QComboBox::event(QEvent*) + 352
22  QtWidgets                       0x103e8389c QApplicationPrivate::notify_helper(QObject*, QEvent*) + 336
23  QtWidgets                       0x103e8531c QApplication::notify(QObject*, QEvent*) + 3260
24  QtCore                          0x104503ff8 QCoreApplication::notifyInternal2(QObject*, QEvent*) + 200
25  QtCore                          0x104505104 QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) + 532
26  libqcocoa.dylib                 0x100c94fa4 0x100c7c000 + 102308
27  libqcocoa.dylib                 0x100c961f0 0x100c7c000 + 106992
28  CoreFoundation                  0x181703a4c __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 28
29  CoreFoundation                  0x1817039e0 __CFRunLoopDoSource0 + 176
30  CoreFoundation                  0x181703750 __CFRunLoopDoSources0 + 244
31  CoreFoundation                  0x181702340 __CFRunLoopRun + 828
32  CoreFoundation                  0x1817019ac CFRunLoopRunSpecific + 608
33  HIToolbox                       0x18bcb0448 RunCurrentEventLoopInMode + 292
34  HIToolbox                       0x18bcb00d8 ReceiveNextEventCommon + 220
35  HIToolbox                       0x18bcaffdc _BlockUntilNextEventMatchingListInModeWithFilter + 76
36  AppKit                          0x184ede8a4 _DPSNextEvent + 660
37  AppKit                          0x1856b8980 -[NSApplication(NSEventRouting) _nextEventMatchingEventMask:untilDate:inMode:dequeue:] + 716
38  AppKit                          0x184ed1d50 -[NSApplication run] + 476
39  libqcocoa.dylib                 0x100c93adc 0x100c7c000 + 96988
40  QtCore                          0x10450dfe0 QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) + 596
41  QtCore                          0x1045047d4 QCoreApplication::exec() + 144
42  labplot                         0x10001bbb4 0x100004000 + 97204
43  dyld                            0x1812a50e0 start + 2360