fix: Gate empty result in GATConv

Author: lenianiva

GNNlib/src/layers/conv.jl

@@ -139,6 +139,9 @@ function gat_conv(l, g::AbstractGNNGraph, x, e::Union{Nothing, AbstractMatrix} =
     α = dropout(α, l.dropout)
     β = α .* m.Wxj
     x = aggregate_neighbors(g, +, β)
+    if isempty(x)
+        return zeros(eltype(x), (length(l.bias), 0))
+    end
 
     if !l.concat
         x = mean(x, dims = 2)