Fix compilation error: taking address of rvalue in dlg_settings_ex.cpp

[Lekhak123]

When compiling florb v1.1 on Fedora 41, encountered a compilation error in dlg_settings_ex.cpp:197:

dlg_settings_ex.cpp:197:88: error: taking address of rvalue [-fpermissive]
m_input_trackwidth->value(static_cast<std::ostringstream*>( &(std::ostringstream() << m_cfgui.tracklinewidth()) )->str().c_str());

The error occurs because the code attempts to take the address of a temporary stringstream object.
Fixed by replacing the problematic line with:

m_input_trackwidth->value(std::to_string(m_cfgui.tracklinewidth()).c_str());

Environment:

• OS: Fedora 41
• Compiler: g++ (version from Fedora 41)
• Build system: omake
• florb version: 1.1