Bail early if all coeffs are emtpy

src/Dofs/ConstraintHandler.jl

@@ -237,7 +237,10 @@ end
 Add the `AffineConstraint` to the `ConstraintHandler`.
 """
 function add!(ch::ConstraintHandler, ac::AffineConstraint)
-    add_prescribed_dof!(ch, ac.constrained_dof, ac.b, isempty(ac.entries) ? nothing : ac.entries)
+    # TODO: Would be nice to pass nothing if ac.entries is empty, but then we lose the fact
+    #       that this constraint is an AffineConstraint which is currently needed in update!
+    #       in order to not update inhomogeneities for affine constraints
+    add_prescribed_dof!(ch, ac.constrained_dof, ac.b, #=isempty(ac.entries) ? nothing : =# ac.entries)
 end
 
 """
@@ -618,7 +621,7 @@ function _condense_sparsity_pattern!(K::SparseMatrixCSC{T}, dofcoefficients::Vec
     ndofs = size(K, 1)
 
     # Return early if there are no non-trivial affine constraints
-    any(i -> i !== nothing, dofcoefficients) || return
+    any(i -> !(i === nothing || isempty(i)), dofcoefficients) || return
 
     # Adding new entries to K is extremely slow, so create a new sparsity triplet for the
     # condensed sparsity pattern
@@ -686,7 +689,7 @@ function _condense!(K::SparseMatrixCSC, f::AbstractVector, dofcoefficients::Vect
     condense_f && @assert( length(f) == ndofs )
 
     # Return early if there are no non-trivial affine constraints
-    any(i -> i !== nothing, dofcoefficients) || return
+    any(i -> !(i === nothing || isempty(i)), dofcoefficients) || return
 
     for col in 1:ndofs
         col_coeffs = coefficients_for_dof(dofmapping, dofcoefficients, col)