Update Torch and Torchvision version placeholders

Updated Torch and Torchvision version placeholders in the configuration.

Author: NeuralFault

StabilityMatrix.Core/Models/Packages/A3WebUI.cs

@@ -227,8 +227,8 @@ torchIndex is TorchIndex.Cuda
         var config = new PipInstallConfig
         {
             RequirementsFilePaths = ["requirements_versions.txt"],
-            TorchVersion = "",
-            TorchvisionVersion = "",
+            TorchVersion = " ",
+            TorchvisionVersion = " ",
             XformersVersion = isLegacyNvidia ? "==0.0.30" : " ",
             CudaIndex = isLegacyNvidia ? "cu126" : "cu128",
             RocmIndex = "rocm7.2",