When a .a or .xcframework path is requested but not found on disk (because
it is already statically linked into the binary), the previous code set
`path = String()` and fell through to `dlopen("")`, which is undefined
behavior and bypasses the RTLD_SELF symbol lookup table used by
`get_dynamic_library_symbol_handle`. This caused GDExtension loading to
fail silently or with ERR_CANT_OPEN when building with vulkan=no on iOS.
Fix by returning RTLD_SELF early, consistent with the existing empty-path
case at the top of the function.
ssd3
44541235ba