Serial Monitor stop working after vscode v1.43 update

[flautines]

Issue Type: Bug

Steps to reproduce the issue:
At the Arduino extension bottom bar click on the "Open Serial Monitor" button.

expected result:
Serial communication is started with the selected compatible board and at the specified COM port.

actual result:
The following error is shown:
Failed to open serial port COM4 due to error: + TypeError: Cannot read property 'close' of null

I made sure the selected port and board was correct by opening the Serial Monitor at the selected port and board from the Arduino IDE.

Extension version: 0.2.29
VS Code version: Code 1.43.1 (fe22a9645b44368865c0ba92e2fb881ff1afce94, 2020-03-18T07:01:20.184Z)
OS version: Windows_NT x64 10.0.18362

System Info

Item	Value
CPUs	Intel(R) Core(TM) i7-6700K CPU @ 4.00GHz (8 x 4008)
GPU Status	2d_canvas: enabled flash_3d: enabled flash_stage3d: enabled flash_stage3d_baseline: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on oop_rasterization: disabled_off protected_video_decode: unavailable_off rasterization: enabled skia_renderer: disabled_off_ok video_decode: enabled viz_display_compositor: enabled_on viz_hit_test_surface_layer: disabled_off_ok webgl: enabled webgl2: enabled
Load (avg)	undefined
Memory (System)	15.96GB (11.69GB free)
Process Argv
Screen Reader	no
VM	0%

[ZiTAL]

#774

[dilin-MS]

Duplicate as #980