DITConfiguration: Prevent a crash if images fail to load

Recently came across a strange issue where Dolphin would hard crash in most games with this error:

```sh
/usr/include/c++/15.2.1/optional:1165: constexpr const _Tp* std::optional<_Tp>::operator->() const [with _Tp = InputCommon::ImagePixelData]: Assertion 'this->_M_is_engaged()' failed.
```

The culprit turned out to be accessing `host_key_image` which is an `std::optional` thay may return `std::nullopt`. I'm not sure why this issue started occuring for me since I've had no issue with my Dynamic Input Textures in the past? But this fixes a crash if the image fails to load.

1 files changed, 9 insertions, 1 deletions

diff --git a/Source/Core/InputCommon/DynamicInputTextures/DITConfiguration.cpp b/Source/Core/InputCommon/DynamicInputTextures/DITConfiguration.cpp
index cced429e81..9ccd98dbc2 100644
--- a/Source/Core/InputCommon/DynamicInputTextures/DITConfiguration.cpp
+++ b/Source/Core/InputCommon/DynamicInputTextures/DITConfiguration.cpp
@@ -150,7 +150,15 @@ void Configuration::GenerateTexture(const Common::IniFile& file,
       }
       else
       {
-        const auto host_key_image = LoadImage(m_base_path + input_image_iter->second);
+        const std::string full_image_path = m_base_path + input_image_iter->second;
+        const auto host_key_image = LoadImage(full_image_path);
+        if (!host_key_image)
+        {
+          ERROR_LOG_FMT(VIDEO,
+                        "Failed to load image '{}' needed for dynamic input texture generation",
+                        full_image_path);
+          continue;
+        }
 
         for (const auto& rect : rects)
         {