Error: Cannot change `multiple` mode of select after initialization

The error is on the image:



My code:

<div fxFlex.gt-lg="100" fxFlex="100" *ngIf="requestAction == 'add'">
<div class="pb-1">
<md2-select placeholder="{{'WidgetType'|translate:lang}}" class="input_custom_width"(change)="widgetNode($event.value)" required>
<md2-option *ngFor="let widgetType of widgetTypeAry" [value]="widgetType.value">
{{widgetType.name}}
</md2-option>
</md2-select>
</div>
</div>
<div fxFlex.gt-lg="100" fxFlex="100" *ngIf="fieldsObj['node'] && showRequestAction" >
<div class="pb-1">
<md2-select placeholder="{{'Node'|translate:lang}}" [formControl]="editWidgetForm.controls['nodeId']" [(ngModel)]="nodeId" class="input_custom_width" [(multiple)]="isMultiNode" (change)="nodeChange($event.value)" required>
<md2-select-header>
<md-input-container class="input_custom_width">
<input mdInput type="text" placeholder="{{'Search'| translate:lang}}" [ngModelOptions]="{standalone: true}" [(ngModel)]="searchNode"/>
</md-input-container>
</md2-select-header>
<md2-option *ngFor="let node of nodesAry | filterPipe : searchNode" [value]="node.value">
{{ node.name }}
</md2-option>
</md2-select>
<small *ngIf="editWidgetForm.controls['nodeId'].hasError('required') && editWidgetForm.controls['nodeId'].touched" class="mat-text-warn">{{'nodeReq'|translate:lang}}</small>
</div>
</div>


When I use the multiple attribute in a select dropdown, it works fine. However, when I use [multiple], it only works in my edit form and not in the add form. I encounter the following error:

Error: Cannot change the multiple mode of select after initialization.
​

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