Crash when removing and re-adding ysfx instance

[AnClark]

I've found another critical bug while using ysfx on REAPER (Windows edition): when I insert a ysfx instance in REAPER FX-Chain, remove it, and re-add it, ysfx will crash.

Tested on the commit 8077347, with MSVC compiler and CMake Debug profile.

Here's a backtrace from LLDB (copied PDB file to the same path of ysfx.vst3 file in advance):

(lldb) target create "reaper"
(lldb) Current executable set to 'C:\Program Files\REAPER (x64)\reaper.exe' (x86_64).
(lldb) run
(lldb) Process 17656 launched: 'C:\Program Files\REAPER (x64)\reaper.exe' (x86_64)
Process 17656 stopped
* thread #1, stop reason = Exception 0x80000003 encountered at address 0x7ffba639a9ac
    frame #0: 0x00007ffba639a9ad ysfx.vst3`juce::SingletonHolder<juce::VBlankDispatcher,juce::DummyCriticalSection,1>::get(this=0x00007ffba6af2088) at juce_Singleton.h:74
   71               {
   72                   // This means that the doNotRecreateAfterDeletion flag was set
   73                   // and you tried to create the singleton more than once.
-> 74                   jassertfalse;
   75                   return nullptr;
   76               }
   77
(lldb) bt
* thread #1, stop reason = Exception 0x80000003 encountered at address 0x7ffba639a9ac
  * frame #0: 0x00007ffba639a9ad ysfx.vst3`juce::SingletonHolder<juce::VBlankDispatcher,juce::DummyCriticalSection,1>::get(this=0x00007ffba6af2088) at juce_Singleton.h:74
    frame #1: 0x00007ffba63ad6a2 ysfx.vst3`juce::VBlankDispatcher::getInstance at juce_win32_Windowing.cpp:1576
    frame #2: 0x00007ffba62ed60f ysfx.vst3`juce::HWNDComponentPeer::HWNDComponentPeer(this=0x0000000013278980) at juce_win32_Windowing.cpp:1660
    frame #3: 0x00007ffba617ab98 ysfx.vst3`juce::Component::createNewPeer at juce_win32_Windowing.cpp:4611
    frame #4: 0x00007ffba6171153 ysfx.vst3`juce::Component::addToDesktop at juce_Component.cpp:721
    frame #5: 0x00007ffba61cd52c ysfx.vst3`juce::TopLevelWindow::TopLevelWindow at juce_TopLevelWindow.cpp:142
    frame #6: 0x00007ffba61d54de ysfx.vst3`juce::ResizableWindow::ResizableWindow at juce_ResizableWindow.cpp:36
    frame #7: 0x00007ffba61d7c13 ysfx.vst3`juce::DocumentWindow::DocumentWindow(this=0x0000000013278610) at juce_DocumentWindow.cpp:52
    frame #8: 0x00007ffba65bdd27 ysfx.vst3`YsfxEditor::Impl::CodeWindow::CodeWindow(this=0x0000000013278610) + 55
    frame #9: 0x00007ffba65b8140 ysfx.vst3`YsfxEditor::Impl::createUI(this=0x00000000135a1e80) at editor.cpp:374
    frame #10: 0x00007ffba65b57cc ysfx.vst3`YsfxEditor::YsfxEditor(this=0x00000000135bb040, proc=0x000000001342d920) at editor.cpp:105
    frame #11: 0x00007ffba654d6b0 ysfx.vst3`YsfxProcessor::createEditor(this=0x000000001342d920) at processor.cpp:292
    frame #12: 0x00007ffba64b89b0 ysfx.vst3`juce::AudioProcessor::createEditorIfNeeded at juce_AudioProcessor.cpp:899
    frame #13: 0x00007ffba5e721a9 ysfx.vst3`juce::JuceVST3EditController::JuceVST3Editor::ContentWrapperComponent::createEditor at juce_VST3_Wrapper.cpp:2037
    frame #14: 0x00007ffba5e71ebc ysfx.vst3`juce::JuceVST3EditController::JuceVST3Editor::createContentWrapperComponentIfNeeded at juce_VST3_Wrapper.cpp:2217
    frame #15: 0x00007ffba5e40491 ysfx.vst3`juce::JuceVST3EditController::JuceVST3Editor::JuceVST3Editor at juce_VST3_Wrapper.cpp:1695
    frame #16: 0x00007ffba5e73332 ysfx.vst3`juce::JuceVST3EditController::createView at juce_VST3_Wrapper.cpp:1218