Close a couple edge case bugs: hadamard and addmm on empty inputs (#2177)

* handle hadamard and addmm on empty inputs

* fix

mlx/ops.cpp

@@ -472,6 +472,10 @@ array hadamard_transform(
     const array& a,
     std::optional<float> scale_ /* = std::nullopt */,
     StreamOrDevice s /* = {} */) {
+  if (a.size() == 0) {
+    throw std::invalid_argument(
+        "[hadamard_transform] Does not support empty arrays.");
+  }
   // Default to an orthonormal Hadamard matrix scaled by 1/sqrt(N)
   int n = a.ndim() > 0 ? a.shape(-1) : 1;
   float scale = scale_.has_value() ? *scale_ : 1.0f / std::sqrt(n);
@@ -4326,6 +4330,10 @@ array addmm(
 
     c = reshape(c, c_reshape, s);
   }
+  if (c.shape() != out_shape) {
+    throw std::invalid_argument(
+        "[addmm] input c must broadcast to the output shape");
+  }
 
   auto out = array(
       std::move(out_shape),