Merge branch 'feature/tt-button-fix' into 'master'

Fixed Error when no additional class was set

See merge request fronk/thetool!804

public/plugins/vue/tt-components/tt-button.js

@@ -30,6 +30,8 @@ Vue.component('tt-button', {
                 'btn-sm': this.sm,
             }
 
+            if (!this.additionalClass) return classes
+
             for (const className of this.additionalClass.split(' ')) {
                 classes[className] = true
             }