[editor] Fix style properties panel conditions

projects/editor/src/app/components/unit-view/page-view/properties/element-style-properties.component.ts

@@ -6,42 +6,42 @@ import {
   selector: 'app-element-style-properties',
   template: `
     <div fxLayout="column">
-      <mat-form-field *ngIf="combinedProperties.backgroundColor"
+      <mat-form-field *ngIf="combinedProperties.backgroundColor != null"
                       appearance="fill" class="mdInput textsingleline">
         <mat-label>Hintergrundfarbe</mat-label>
         <input matInput type="color" [value]="combinedProperties.backgroundColor"
                (input)="updateModel.emit({ property: 'backgroundColor', value: $any($event.target).value })">
       </mat-form-field>
-      <mat-form-field *ngIf="combinedProperties.fontColor"
+      <mat-form-field *ngIf="combinedProperties.fontColor != null"
                       appearance="fill" class="mdInput textsingleline">
         <mat-label>Schriftfarbe</mat-label>
         <input matInput type="color" [value]="combinedProperties.fontColor"
                (input)="updateModel.emit({ property: 'fontColor', value: $any($event.target).value })">
       </mat-form-field>
-      <mat-form-field *ngIf="combinedProperties.font"
+      <mat-form-field *ngIf="combinedProperties.font != null"
                       appearance="fill" class="mdInput textsingleline">
         <mat-label>Schriftart</mat-label>
         <input matInput type="text" [value]="combinedProperties.font"
                (input)="updateModel.emit({ property: 'font', value: $any($event.target).value })">
       </mat-form-field>
-      <mat-form-field *ngIf="combinedProperties.fontSize"
+      <mat-form-field *ngIf="combinedProperties.fontSize != null"
                       appearance="fill" class="mdInput textsingleline">
         <mat-label>Schriftgröße</mat-label>
         <input matInput type="text" [value]="combinedProperties.fontSize"
                (input)="updateModel.emit({ property: 'fontSize', value: $any($event.target).value })">
       </mat-form-field>
 
-      <mat-checkbox *ngIf="combinedProperties.bold"
+      <mat-checkbox *ngIf="combinedProperties.bold != null"
                     [checked]="$any(combinedProperties.bold)"
                     (change)="updateModel.emit({ property: 'bold', value: $event.checked })">
         Fett
       </mat-checkbox>
-      <mat-checkbox *ngIf="combinedProperties.italic"
+      <mat-checkbox *ngIf="combinedProperties.italic != null"
                     [checked]="$any(combinedProperties.italic)"
                     (change)="updateModel.emit({ property: 'italic', value: $event.checked })">
         Kursiv
       </mat-checkbox>
-      <mat-checkbox *ngIf="combinedProperties.underline"
+      <mat-checkbox *ngIf="combinedProperties.underline != null"
                     [checked]="$any(combinedProperties.underline)"
                     (change)="updateModel.emit({ property: 'underline', value: $event.checked })">
         Unterstrichen