fixing missing variable

include/aidge/backend/cpu/operator/MaxPoolingImpl_forward_kernels.hpp

@@ -73,6 +73,7 @@ void MaxPoolingImpl2D_cpu_forward_kernel(const MaxPooling_Op<2>::Parameters &par
                     const std::size_t iy = oy * std::get<0>(params)[1];
 
                     I poolValue(0.0);
+                    bool valid = false;
 
                     for (unsigned int channel = 0; channel < dims[1];
                             ++channel){