Editor crashes, quits when clicking on Preferences, or Preview (Linux)

[marek-lach]

(thiefmd:309314): GtkSourceView-WARNING **: 16:13:52.905: in file /usr/share/com.github.kmwallio.thiefmd/gtksourceview-4/language-specs/latex.lang: style 'def:text' not defined

(thiefmd:309314): GtkSourceView-WARNING **: 16:13:52.905: in file /usr/share/com.github.kmwallio.thiefmd/gtksourceview-4/language-specs/latex.lang: style 'def:text' not defined

(thiefmd:309314): GtkSourceView-WARNING **: 16:13:52.905: in file /usr/share/com.github.kmwallio.thiefmd/gtksourceview-4/language-specs/latex.lang: style 'def:text' not defined

(thiefmd:309314): libenchant-WARNING **: 16:13:52.978: Error loading plugin: libaspell.so.15: cannot open shared object file: No such file or directory

(thiefmd:309314): libenchant-WARNING **: 16:13:52.979: Error loading plugin: libvoikko.so.1: cannot open shared object file: No such file or directory

(thiefmd:309314): libenchant-WARNING **: 16:13:52.979: Error loading plugin: libhspell.so.0: cannot open shared object file: No such file or directory

This error occurs regardless of whether spellchecking is turned on, or off.
(thiefmd:309314): libenchant-WARNING **: 16:13:52.979: Error loading plugin: libnuspell.so.5: cannot open shared object file: No such file or directory

** (thiefmd:309314): WARNING **: 16:13:53.003: Editor.vala:583: enchant error for language: en_GB.UTF-8

** (thiefmd:309314): WARNING **: 16:13:53.028: Editor.vala:583: enchant error for language: en_GB.UTF-8

** (thiefmd:309314): WARNING **: 16:13:53.054: Editor.vala:583: enchant error for language: en_GB.UTF-8

** (thiefmd:309314): WARNING **: 16:13:53.080: Editor.vala:583: enchant error for language: en_GB.UTF-8

** (thiefmd:309314): WARNING **: 16:13:53.108: Editor.vala:583: enchant error for language: en_GB.UTF-8

** (thiefmd:309314): WARNING **: 16:13:53.135: Editor.vala:583: enchant error for language: en_GB.UTF-8

** (thiefmd:309314): CRITICAL **: 16:13:53.164: check_range: assertion 'spell->priv->speller != NULL' failed
link-grammar: Info: Dictionary found at /usr/share/link-grammar/en/4.0.dict
link-grammar: Info: en: Spell checker disabled.
link-grammar: Info: Dictionary found at /usr/share/link-grammar/en/4.0.dict
link-grammar: Info: en: Spell checker disabled.

** (thiefmd:309314): WARNING **: 16:13:53.641: Editor.vala:583: enchant error for language: en_GB.UTF-8

** (thiefmd:309314): WARNING **: 16:13:53.695: Editor.vala:583: enchant error for language: en_GB.UTF-8
Segmentation fault (core dumped)

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This error happens regardless of whether spellchecking is turned on, or off. Possibly related #187.