Linux Installer and Gtk errors

After upgrading Arduino from version 1.8.10 to 1.8.12 using the `install.sh` script (from the 1.8.12 version), I noticed that I could not use terminator anymore (early crashing with a Gtk error as output)

In xterm:

```text
$> terminator

> (terminator:12853): Gtk-WARNING **: 09:02:59.417: Could not load a pixbuf from icon theme.
> This may indicate that pixbuf loaders or the mime database could not be found.
> **
> Gtk:ERROR:../../../../gtk/gtkiconhelper.c:494:ensure_surface_for_gicon: assertion failed (error == NULL): Failed to load /usr/share/icons/Adwaita/16x16/status/image-missing.png: Unrecognized image file format (gdk-pixbuf-error-quark, 3)
> Aborted
```

I had similar problems with gimp

```text
> (gimp:12377): GdkPixbuf-CRITICAL **: 08:56:27.099: gdk_pixbuf_get_n_channels: assertion 'GDK_IS_PIXBUF (pixbuf)' failed
```

The involved file `/usr/share/icons/Adwaita/16x16/status/image-missing.png` existed
After a reboot, my window manager (i3) did not start anymore

These did not work:

```text
$> update-mime-database ~/.local/share/mime
```

```text
$> sudo update-mime-database /root/.local/share/mime
```

The fix:

```text
sudo apt-get install --reinstall shared-mime-info
```

I can reproduce the issue re-running the install.sh script and appended the output file of the following:

```text
sudo bash -x ./install.sh > log_arduino_install_1.8.12 2>&1
```

[log_arduino_install_1.8.12.txt](https://github.com/arduino/Arduino/files/4347774/log_arduino_install_1.8.12.txt)

os:

```text
$> lsb_release -a
> No LSB modules are available.
> Distributor ID: Debian
> Description: Debian GNU/Linux 10 (buster)
> Release: 10
> Codename: buster

uname
4.19.0-5-amd64 #1 SMP Debian 4.19.37-5+deb10u2 (2019-08-08) x86_64 GNU/Linux

$> bash --version | head -n 1
> GNU bash, version 5.0.3(1)-release (x86_64-pc-linux-gnu)
```

Start with install.sh and the attached log_arduino_install_1.8.12.txt, reproducing the report on Debian 10 with the stated Arduino IDE versions. Trace the installer steps related to the reported GTK and shared-mime-info failures; done means the installer no longer causes the terminator, GIMP, or i3 failures described in the issue.

Written by the indexing model from the issue text.