DRC fails to detect copper polygon in footprint short-circuiting pads or tracks

Description

When a copper polygon is a part of a footprint, the DRC does not detect shorts of tracks or pads (even with extended options of DRC set). Expected behaviour is that all unintended short-circuits are detected by DRC.

Steps to reproduce

1. Place a footprint containing copper polygon to board so that it shorts tracks or pads of different net.
2. Tick DRC options:

• Report all errors for tracks (slower)
• Test tracks against filled copper areas (very slow)

3. Run DRC

KiCad Version

Application: KiCad
Version: 5.1.8+dfsg1-1~bpo10+1, release build
Libraries:
    wxWidgets 3.0.4
    libcurl/7.64.0 OpenSSL/1.1.1d zlib/1.2.11 libidn2/2.0.5 libpsl/0.20.2 (+libidn2/2.0.5) libssh2/1.8.0 nghttp2/1.36.0 librtmp/2.3
Platform: Linux 4.19.0-12-amd64 x86_64, 64 bit, Little endian, wxGTK
Build Info:
    wxWidgets: 3.0.4 (wchar_t,wx containers,compatible with 2.8) GTK+ 3.24
    Boost: 1.67.0
    OpenCASCADE Technology: 7.3.0
    Curl: 7.64.0
    Compiler: GCC 8.3.0 with C++ ABI 1013

Build settings:
    USE_WX_GRAPHICS_CONTEXT=OFF
    USE_WX_OVERLAY=ON
    KICAD_SCRIPTING=ON
    KICAD_SCRIPTING_MODULES=ON
    KICAD_SCRIPTING_PYTHON3=ON
    KICAD_SCRIPTING_WXPYTHON=ON
    KICAD_SCRIPTING_WXPYTHON_PHOENIX=ON
    KICAD_SCRIPTING_ACTION_MENU=ON
    BUILD_GITHUB_PLUGIN=ON
    KICAD_USE_OCE=OFF
    KICAD_USE_OCC=ON
    KICAD_SPICE=ON