Guard listener cleanup of BasicProviderImpl

Otherwise JunitTest_sfx2_complex dbgutil asserts especially on
Windows with:

ucrtbased!get_wide_winmain_command_line+0x296
ucrtbased!get_wide_winmain_command_line+0xe4
ucrtbased!wassert+0x1a
vcllo!ImplDbgTestSolarMutex+0x43
tllo!DbgTestSolarMutex+0x11d
svllo!SfxBroadcaster::RemoveListener+0x2e
svllo!SfxListener::~SfxListener+0x8f
basprovlo!basprov::BasicProviderImpl::~BasicProviderImpl+0x8f
...

Change-Id: Ia183436a92bc70ed5208364987b3e97e27b5bd6e
Reviewed-on: https://gerrit.libreoffice.org/63289
Reviewed-by: Michael Stahl <Michael.Stahl@cib.de>
Tested-by: Jenkins
diff --git a/scripting/source/basprov/basprov.cxx b/scripting/source/basprov/basprov.cxx
index 6c856d5..1055b57 100644
--- a/scripting/source/basprov/basprov.cxx
+++ b/scripting/source/basprov/basprov.cxx
@@ -101,6 +101,8 @@ namespace basprov

    BasicProviderImpl::~BasicProviderImpl()
    {
        SolarMutexGuard aGuard;
        EndListeningAll();
    }