Memory leakage on re-import

[2shady4u]

Plugin version
v2.3
Godot version 3.2.1 (Stable)

Issue description
Export through command line (without .import-folder) results in memory leakage.

Steps to reproduce

• Make a new Godot project and add the latest godot-tiled-importer addon from the assetlib
• Add a tilemap TMX file containing at least one PNG (that is also present in the project hierarchy)
• Add a node with a TMX instance of your tilemap
• Make an export preset for Windows
• Set verbose_output to true in the ProjectSettings
• Export the game through the command line with:
  godot -v --export-debug "Windows Desktop" build/test.exe

Look at the verbose output:

All good 👌

Now DELETE the .import-folder and repeat this command in the console, and you will get this:

Notice the memory leakage 😢

Example project
test-tiled-ci.zip

How could this be fixed?