Fix assertion error when printing an empty Tensor.

include/aidge/data/Tensor.hpp

@@ -391,7 +391,7 @@ class Tensor : public Data,
 
 
     std::string toString() const {
-        AIDGE_ASSERT(mImpl && mImpl->hostPtr() != nullptr, "tensor should have a valid host pointer");
+        AIDGE_ASSERT(mImpl && (dims().empty() || (dims() == std::vector<DimSize_t>({0})) || (mImpl->hostPtr() != nullptr)), "tensor should have a valid host pointer");
 
         // TODO: move lambda elsewhere?
         auto ptrToString = [](DataType dt, void* ptr, size_t idx) {
@@ -471,7 +471,7 @@ class Tensor : public Data,
         } else {
             res += "{";
             for (DimSize_t j = 0; j < dims()[0]; ++j) {
-                res += " " + ptrToString(mDataType, mImpl->hostPtr(), j) + ((j < dims()[0]-1) ? "," : "");
+                res += " " + ptrToString(mDataType, mImpl->hostPtr(), j) + ((j < dims()[0]-1) ? "," : " ");
             }
         }
         res += "}";