LO building fails with non debug mode on slideshow/source/engine/box2dtools.cxx (loplugin:staticmethods)

Hello Sarper and Thorsten,

On pc Debian x86-64 with master sources updated today with non debug 
build, I got these building errors:

In file included from 
/home/julien/lo/libo_perf/slideshow/source/engine/box2dtools.cxx:10:
/home/julien/lo/libo_perf/slideshow/source/inc/box2dtools.hxx:212:24: 
error: this member function can be declared static [loplugin:staticmethods]
    Box2DBodySharedPtr makeBodyDynamic(const Box2DBodySharedPtr& 
pBox2DBody);
~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/julien/lo/libo_perf/slideshow/source/engine/box2dtools.cxx:370:32: 
note: defined here: [loplugin:staticmethods]
Box2DBodySharedPtr box2DWorld::makeBodyDynamic(const Box2DBodySharedPtr& 
pBox2DBody)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from 
/home/julien/lo/libo_perf/slideshow/source/engine/box2dtools.cxx:10:
/home/julien/lo/libo_perf/slideshow/source/inc/box2dtools.hxx:230:24: 
error: this member function can be declared static [loplugin:staticmethods]
    Box2DBodySharedPtr makeBodyStatic(const Box2DBodySharedPtr& 
pBox2DBody);
~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/julien/lo/libo_perf/slideshow/source/engine/box2dtools.cxx:387:32: 
note: defined here: [loplugin:staticmethods]
Box2DBodySharedPtr box2DWorld::makeBodyStatic(const Box2DBodySharedPtr& 
pBox2DBody)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I don't reproduce this with my build containing enable-dbgutil because 
the functions contain:

assert(mpBox2DWorld);

For the rest, they can indeed be static, see 
https://opengrok.libreoffice.org/xref/core/slideshow/source/engine/box2dtools.cxx?r=28022cee&mo=12079&fi=370#370

and 
https://opengrok.libreoffice.org/xref/core/slideshow/source/engine/box2dtools.cxx?r=28022cee&mo=12079&fi=387#387

Julien