fix: validate BayesianDenseLayer batch dimension

Author: ooples

src/UncertaintyQuantification/Layers/BayesianDenseLayer.cs

@@ -229,11 +229,19 @@ public override Tensor<T> Forward(Tensor<T> input)
             SampleWeights();
         }
 
-        var batch = input.Rank == 1 ? 1 : input.Shape[0];
-        if (batch <= 0)
+        int batch;
+        if (input.Rank == 1)
         {
             batch = 1;
         }
+        else
+        {
+            batch = input.Shape[0];
+            if (batch <= 0)
+            {
+                throw new ArgumentException("Expected input tensor to have a positive batch dimension (Shape[0]).", nameof(input));
+            }
+        }
 
         var expectedLength = batch * _inputSize;
         if (input.Length != expectedLength)
@@ -275,11 +283,19 @@ public override Tensor<T> Backward(Tensor<T> outputGradient)
         if (_lastInput == null || _sampledWeights == null || _lastPreActivation == null)
             throw new InvalidOperationException("Forward pass must be called before backward pass.");
 
-        var batch = _lastInput.Rank == 1 ? 1 : _lastInput.Shape[0];
-        if (batch <= 0)
+        int batch;
+        if (_lastInput.Rank == 1)
         {
             batch = 1;
         }
+        else
+        {
+            batch = _lastInput.Shape[0];
+            if (batch <= 0)
+            {
+                throw new ArgumentException("Expected last input tensor to have a positive batch dimension (Shape[0]).", nameof(outputGradient));
+            }
+        }
 
         var expectedGradientLength = batch * _outputSize;
         if (outputGradient.Length != expectedGradientLength)