Fix not initialized m_pFilterPanel pointer

[Masterkatze]

Description

m_pFilterPanel pointer is not initialized by default, which can skip memory allocation under if ( m_pFilterPanel == NULL ) check, and then we use it in m_pFilterPanel->SetVisible( false );

Toolchain

• Linux GCC Distro Native [Arch Linux, g++ (GCC) 16.1.1 20260430]

Linked Issues

• fixes Crash when loading into a map (release build, gcc 16.1.1) #1977

[AdamTadeusz]

ifdef neo? nullptr? Could also initialize the nullptr in the header