[fix] split different if conditions

we used conditionals of the form

if (isset Foo "bar") and (check-content Foo.bar)

This used to work similar to C or C++, where the seond ondition is only evaluated, when the first condition is true.

It seems that this is not the case anymore and newer hugo versions fail because they try to evaluate check-content even if Foo.bar is not defined.

We now simply split the two conditions into two separate ifs.

This fixes #86