Resolve "Réorganisation criterion (null, not null)"

Closes #41 (closed)

client/src/app/instance/search/components/criteria/search-type/date.component.html

 <form [formGroup]="form" novalidate>
     <div class="row form-group">
         <div class="col-md-3 col-sm-auto pr-sm-1 mb-1 mb-sm-0">
-            <select class="custom-select" formControlName="operator">
+            <select class="custom-select" formControlName="operator" (change)="operatorOnChange()">
                 <option *ngFor="let o of operators" [ngValue]="o.value">{{ o.label }}</option>
             </select>
         </div>