Fix #140562: Cycles crash with texture in custom camera with SVM on GPU

After spending way too much time looking into the image handle code
because I assumed the issue is some interaction between OSL code using
a texture and the image system that's in SVM mode (which never happened
before the custom camera) with printf debuggine because OptiX doesn't
work in debug builds, it turns out the issue was something else entirely:
C++ iterator bullshit.

Specifically, when we remove an entry from services->textures, this
invalidates the iterator, so the code restarts from the beginning.
However, the for-loop still increments the iterator *before* checking
the termination criterion.
If we remove the only element of the map, we:
- Set it = map.begin(), which equals map.end() since it's empty now
- Increment it at the end of the loop iteration
- Compare it == map.end(), which is wrong now since we're past the end

No idea how this didn't blow up sooner, none of this seems camera-specific??
Anyways, the fix is simple - only increment if we didn't restart.

Pull Request: https://projects.blender.org/blender/blender/pulls/141580

intern/cycles/scene/osl.cpp

@@ -286,7 +286,7 @@ void OSLManager::device_free(Device *device, DeviceScene * /*dscene*/, Scene *sc
   /* Remove any textures specific to an image manager from shared render services textures, since
    * the image manager may get destroyed next. */
   foreach_render_services([scene](OSLRenderServices *services) {
-    for (auto it = services->textures.begin(); it != services->textures.end(); ++it) {
+    for (auto it = services->textures.begin(); it != services->textures.end();) {
       if (it->second.handle.get_manager() == scene->image_manager.get()) {
         /* Don't lock again, since the iterator already did so. */
         services->textures.erase(it->first, false);
@@ -294,6 +294,9 @@ void OSLManager::device_free(Device *device, DeviceScene * /*dscene*/, Scene *sc
         /* Iterator was invalidated, start from the beginning again. */
         it = services->textures.begin();
       }
+      else {
+        ++it;
+      }
     }
   });
 }