Plotting HPGL in eeschema crashes

UPDATE: It was plotting HPGL, not using a text variable.

Description

Using a text replacement variable in eeschema Plot Schematic dialog Output directory field makes KiCad crash.

It works correctly in pcbnew.

Steps to reproduce

1. Add a variable to Text Variables.
2. In eeschema open the Plot Schematic dialog.
3. Use the text variable in the Output directory.
4. Accept the dialog.
5. Crash

KiCad Version

Application: Eeschema
Version: (5.99.0-1808-g8226e5f0e), release build
Libraries:
    wxWidgets 3.0.4
    libcurl/7.66.0 OpenSSL/1.1.1d (Schannel) zlib/1.2.11 brotli/1.0.7 libidn2/2.2.0 libpsl/0.21.0 (+libidn2/2.1.1) nghttp2/1.39.2
Platform: Windows 8 (build 9200), 64-bit edition, 64 bit, Little endian, wxMSW
Build Info:
    Build date: May 26 2020 23:03:28
    wxWidgets: 3.0.4 (wchar_t,wx containers,compatible with 2.8)
    Boost: 1.71.0
    OpenCASCADE Community Edition: 6.9.1
    Curl: 7.66.0
    Compiler: GCC 9.2.0 with C++ ABI 1013

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