Kernel: Use Userspace<T> for the execve syscall

Author: https://github.com/bgianfo
Commit: 0f42463eab
Pull-request: https://github.com/SerenityOS/serenity/pull/3062
Reviewed-by: https://github.com/awesomekling

DevTools/UserspaceEmulator/Emulator.cpp

@@ -957,7 +957,7 @@ int Emulator::virt$execve(FlatPtr params_addr)
     auto copy_string_list = [this](auto& output_vector, auto& string_list) {
         for (size_t i = 0; i < string_list.length; ++i) {
             Syscall::StringArgument string;
-            mmu().copy_from_vm(&string, (FlatPtr)&string_list.strings[i], sizeof(string));
+            mmu().copy_from_vm(&string, (FlatPtr)&string_list.strings.ptr()[i], sizeof(string));
             output_vector.append(String::copy(mmu().copy_buffer_from_vm((FlatPtr)string.characters, string.length)));
         }
     };