fix Slice warning

src/operator/Slice.cpp

@@ -152,7 +152,7 @@ bool Aidge::Slice_Op::forwardDims(bool /*allowDataDependency*/) {
             if(step == 0) {
                 AIDGE_THROW_OR_ABORT(std::runtime_error, "{}: Step must be a non-zero value", type());
             }
-            if(step * (end - start) < 0) {
+            if(step * (static_cast<int64_t>(end) - static_cast<int64_t>(start)) < 0) {
                 if(step < 0) {
                     AIDGE_THROW_OR_ABORT(std::runtime_error, "{}: Step is negative we must have End < Start", type());
                 }