windterm 2.6.1 crash when switch ssh tab session, and can be reproduced

Got stacktrace from gdb:
```
Thread 1 "WindTerm" received signal SIGSEGV, Segmentation fault.
0x00007ffff3acf63f in QObject::startTimer(int, Qt::TimerType) () from /home/debian/WindTerm_2.6.1/lib/libQt5Core.so.5
(gdb) bt
#0 0x00007ffff3acf63f in QObject::startTimer(int, Qt::TimerType) () at /home/debian/WindTerm_2.6.1/lib/libQt5Core.so.5
#1 0x00007ffff3adaceb in QTimer::start() () at /home/debian/WindTerm_2.6.1/lib/libQt5Core.so.5
#2 0x00000000007e4138 in ()
#3 0x00000000007e84ca in ()
#4 0x00000000007910e1 in ()
#5 0x00007ffff3accda3 in QObject::event(QEvent*) () at /home/debian/WindTerm_2.6.1/lib/libQt5Core.so.5
#6 0x00007ffff5f6343c in QApplicationPrivate::notify_helper(QObject*, QEvent*) () at /home/debian/WindTerm_2.6.1/lib/libQt5Widgets.so.5
#7 0x00007ffff5f69f20 in QApplication::notify(QObject*, QEvent*) () at /home/debian/WindTerm_2.6.1/lib/libQt5Widgets.so.5
#8 0x00007ffff3a9d808 in QCoreApplication::notifyInternal2(QObject*, QEvent*) () at /home/debian/WindTerm_2.6.1/lib/libQt5Core.so.5
#9 0x00007ffff3aa0882 in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) () at /home/debian/WindTerm_2.6.1/lib/libQt5Core.so.5
#10 0x00007ffff3af9b33 in () at /home/debian/WindTerm_2.6.1/lib/libQt5Core.so.5
#11 0x00007ffff731c7a9 in g_main_context_dispatch () at /lib/x86_64-linux-gnu/libglib-2.0.so.0
#12 0x00007ffff731ca38 in () at /lib/x86_64-linux-gnu/libglib-2.0.so.0
#13 0x00007ffff731cacc in g_main_context_iteration () at /lib/x86_64-linux-gnu/libglib-2.0.so.0
#14 0x00007ffff3af91cc in QEventDispatcherGlib::processEvents(QFlags) () at /home/debian/WindTerm_2.6.1/lib/libQt5Core.so.5
#15 0x00007ffff3a9c21a in QEventLoop::exec(QFlags) () at /home/debian/WindTerm_2.6.1/lib/libQt5Core.so.5
#16 0x00007ffff3aa51d3 in QCoreApplication::exec() () at /home/debian/WindTerm_2.6.1/lib/libQt5Core.so.5
#17 0x00000000004e657d in main ()
```

Reproduce the crash by switching SSH tab sessions in WindTerm 2.6.1 under gdb, then begin at the reported main entry point and inspect the unnamed frames leading to QTimer::start(). Confirm the fix by repeating the tab switch workflow and verifying that the SIGSEGV no longer occurs.

Written by the indexing model from the issue text.