'let' breaks closure (when used with makeGetValue)

Author: cwoffenden

src/lib/libwebaudio.js

@@ -222,7 +222,7 @@ let LibraryWebAudio = {
     assert(EmAudio[contextHandle] instanceof (window.AudioContext || window.webkitAudioContext), `Called emscripten_create_wasm_audio_worklet_processor_async() on a context handle ${contextHandle} that is not an AudioContext, but of type ${typeof EmAudio[contextHandle]}`);
 #endif
 
-    let audioParams = [],
+    var audioParams = [],
       processorName = UTF8ToString({{{ makeGetValue('options', C_STRUCTS.WebAudioWorkletProcessorCreateOptions.name, '*') }}}),
       numAudioParams = {{{ makeGetValue('options', C_STRUCTS.WebAudioWorkletProcessorCreateOptions.numAudioParams, 'i32') }}},
       audioParamDescriptors = {{{ makeGetValue('options', C_STRUCTS.WebAudioWorkletProcessorCreateOptions.audioParamDescriptors, '*') }}},