This silences warnings like
/home/mkuron/squirmer/src/core/math/Quaternion.h: In instantiation of 'walberla::math::Quaternion<Type>& walberla::math::Quaternion<T>::normalize() [with Type = double]':
/home/mkuron/squirmer/apps/squirmer/Squirmer.cpp:185:22: required from here
/home/mkuron/squirmer/src/core/math/Quaternion.h:521:12: warning: comparing floating point with == or != is unsafe [-Wfloat-equal]
if( len == Type(0) )