[Critical Bug] Furnace crashes on renaming instrument with non standard symbols in name

[freq-mod]

backup.fur.zip - backup module.

STEPS TO REPRODUCE:

1. Load this module
2. Select Instrument 1 (the one with funny chars, imported from FF bank)
3. Highlight the name
4. Press any key you like

furnace: /home/anon/furnace/extern/imgui_patched/imgui_widgets.cpp:4548: bool ImGui::InputTextEx(const char*, const char*, char*, int, const ImVec2&, ImGuiInputTextFlags, ImGuiInputTextCallback, void*): Assertion `apply_new_text_length >= 0' failed.
Stack trace (most recent call last):
#12 Object "[0xffffffffffffffff]", at 0xffffffffffffffff, in
#11 Object "furnace", at 0x5604fb6b32b9, in _start
#10 Object "/lib/x86_64-linux-gnu/libc.so.6", at 0x7f45bd84a7fc, in __libc_start_main
#9 Object "furnace", at 0x5604fb8d1cc8, in main
#8 Object "furnace", at 0x5604fbacf650, in FurnaceGUI::loop()
#7 Object "furnace", at 0x5604fba3238a, in FurnaceGUI::drawInsEdit()
#6 Object "furnace", at 0x5604fb99c468, in ImGui::InputText(char const*, std::__cxx11::basic_string<char, std::char_traits, std::allocator >, int, int ()(ImGuiInputTextCallbackData*), void*)
#5 Object "furnace", at 0x5604fb974fec, in ImGui::InputText(char const*, char*, unsigned long, int, int ()(ImGuiInputTextCallbackData), void*)
#4 Object "furnace", at 0x5604fb97b699, in ImGui::InputTextEx(char const*, char const*, char*, int, ImVec2 const&, int, int ()(ImGuiInputTextCallbackData), void*)
#3 Object "/lib/x86_64-linux-gnu/libc.so.6", at 0x7f45bd858221, in __assert_fail
#2 Object "/lib/x86_64-linux-gnu/libc.so.6", at 0x7f45bd84942e, in
#1 Object "/lib/x86_64-linux-gnu/libc.so.6", at 0x7f45bd849545, in abort
#0 Object "/lib/x86_64-linux-gnu/libc.so.6", at 0x7f45bd85f8a1, in gsignal
Aborted (Signal sent by tkill() 26422 1000)

[tildearrow]

Applied a possible fix.