The plugin was indeed in the dependencies section even though it was not installed on my nodeBB instance, weird.
Removing it has fixed the error. Thank you so much for your help 
Here's how the package.json file looked like:
{
"name": "nodebb",
"license": "GPL-3.0",
"description": "NodeBB Forum",
"version": "1.16.1",
"homepage": "http://www.nodebb.org",
"repository": {
"type": "git",
"url": "https://github.com/NodeBB/NodeBB/"
},
"main": "app.js",
"scripts": {
"start": "node loader.js",
"lint": "npx eslint --cache ./nodebb .",
"test": "npx nyc --reporter=html --reporter=text-summary npx mocha",
"coverage": "nyc report --reporter=text-lcov > ./coverage/lcov.info",
"coveralls": "nyc report --reporter=text-lcov | coveralls && rm -r coverage"
},
"husky": {
"hooks": {
"pre-commit": "npx lint-staged",
"commit-msg": "npx commitlint -E HUSKY_GIT_PARAMS"
}
},
"lint-staged": {
"*.js": [
"eslint --fix",
"git add"
]
},
"dependencies": {
"@adactive/bootstrap-tagsinput": "^0.8.2",
"@nodebb/bootswatch": "3.4.2",
"ace-builds": "^1.4.9",
"archiver": "^5.0.0",
"async": "^3.2.0",
"autoprefixer": "10.2.0",
"bcryptjs": "2.4.3",
"benchpressjs": "2.4.0",
"body-parser": "^1.19.0",
"bootbox": "4.4.0",
"bootstrap": "^3.4.1",
"chart.js": "^2.9.3",
"cli-graph": "^3.2.2",
"clipboard": "^2.0.6",
"colors": "^1.4.0",
"commander": "^6.0.0",
"compare-versions": "3.6.0",
"compression": "^1.7.4",
"connect-ensure-login": "^0.1.1",
"connect-flash": "^0.1.1",
"connect-mongo": "3.2.0",
"connect-multiparty": "^2.2.0",
"connect-pg-simple": "^6.1.0",
"connect-redis": "5.0.0",
"cookie-parser": "^1.4.5",
"cron": "^1.8.2",
"cropperjs": "^1.5.6",
"csurf": "^1.11.0",
"daemon": "^1.1.0",
"diff": "^5.0.0",
"express": "^4.17.1",
"express-session": "^1.17.0",
"express-useragent": "^1.0.13",
"graceful-fs": "^4.2.3",
"helmet": "^4.0.0",
"html-to-text": "6.0.0",
"ipaddr.js": "^2.0.0",
"jquery": "3.5.1",
"jquery-deserialize": "2.0.0-rc1",
"jquery-form": "4.3.0",
"jquery-serializeobject": "1.0.0",
"jquery-ui": "1.12.1",
"jsesc": "3.0.2",
"json2csv": "5.0.5",
"jsonwebtoken": "^8.5.1",
"less": "^3.11.1",
"lodash": "^4.17.15",
"logrotate-stream": "^0.2.6",
"lru-cache": "6.0.0",
"material-design-lite": "^1.3.0",
"mime": "^2.4.4",
"mkdirp": "^1.0.4",
"mongodb": "3.6.3",
"morgan": "^1.10.0",
"mousetrap": "^1.6.5",
"nconf": "^0.11.0",
"nodebb-plugin-composer-default": "6.5.5",
"nodebb-plugin-dbsearch": "4.1.2",
"nodebb-plugin-emoji": "^3.3.0",
"nodebb-plugin-emoji-android": "2.0.0",
"nodebb-plugin-gamification": "^1.0.1",
"nodebb-plugin-markdown": "8.12.4",
"nodebb-plugin-mentions": "2.13.6",
"nodebb-plugin-question-and-answer": "^0.7.7",
"nodebb-plugin-require": "0.0.6",
"nodebb-plugin-seo": "^1.0.0",
"nodebb-plugin-seo-slug-friendly": "0.0.8",
"nodebb-plugin-seo-thread": "^0.1.10",
"nodebb-plugin-soundpack-default": "1.0.0",
"nodebb-plugin-spam-be-gone": "0.7.7",
"nodebb-rewards-essentials": "0.1.4",
"nodebb-theme-lavender": "5.0.17",
"nodebb-theme-persona": "10.3.17",
"nodebb-theme-slick": "1.3.7",
"nodebb-theme-vanilla": "11.3.10",
"nodebb-widget-essentials": "5.0.2",
"nodemailer": "^6.4.6",
"nprogress": "0.2.0",
"passport": "^0.4.1",
"passport-http-bearer": "^1.0.1",
"passport-local": "1.0.0",
"pg": "^8.0.2",
"pg-cursor": "^2.1.9",
"postcss": "8.1.10",
"postcss-clean": "1.1.0",
"promise-polyfill": "^8.1.3",
"prompt": "^1.0.0",
"redis": "3.0.2",
"request": "2.88.2",
"request-promise-native": "^1.0.8",
"requirejs": "2.3.6",
"rimraf": "3.0.2",
"rss": "^1.2.2",
"sanitize-html": "^2.0.0",
"semver": "^7.2.1",
"serve-favicon": "^2.5.0",
"sharp": "0.27.0",
"sitemap": "^6.1.0",
"slideout": "1.0.1",
"socket.io": "3.0.5",
"socket.io-adapter-cluster": "^1.0.1",
"socket.io-client": "3.0.5",
"socket.io-redis": "6.0.1",
"sortablejs": "1.10.2",
"spdx-license-list": "^6.1.0",
"spider-detector": "2.0.0",
"textcomplete": "^0.17.1",
"textcomplete.contenteditable": "^0.1.1",
"timeago": "^1.6.7",
"tinycon": "0.6.8",
"toobusy-js": "^0.5.1",
"uglify-es": "^3.3.9",
"validator": "13.5.2",
"visibilityjs": "2.0.2",
"winston": "3.3.3",
"xml": "^1.0.1",
"xregexp": "^4.3.0",
"zxcvbn": "^4.4.2"
},
"devDependencies": {
"@apidevtools/swagger-parser": "10.0.2",
"@commitlint/cli": "11.0.0",
"@commitlint/config-angular": "11.0.0",
"coveralls": "3.1.0",
"eslint": "7.17.0",
"eslint-config-airbnb-base": "14.2.1",
"eslint-plugin-import": "2.22.1",
"grunt": "1.3.0",
"grunt-contrib-watch": "1.1.0",
"husky": "4.3.6",
"jsdom": "16.4.0",
"lint-staged": "10.5.3",
"mocha": "8.2.1",
"mocha-lcov-reporter": "1.3.0",
"nyc": "15.1.0",
"smtp-server": "3.8.0"
},
"bugs": {
"url": "https://github.com/NodeBB/NodeBB/issues"
},
"engines": {
"node": ">=10"
},
"maintainers": [
{
"name": "Andrew Rodrigues",
"email": "andrew@nodebb.org",
"url": "https://github.com/psychobunny"
},
{
"name": "Julian Lam",
"email": "julian@nodebb.org",
"url": "https://github.com/julianlam"
},
{
"name": "Barış Soner Uşaklı",
"email": "baris@nodebb.org",
"url": "https://github.com/barisusakli"
}
],
"nyc": {
"exclude": [
"src/upgrades/*",
"test/*"
]
}
}
