fix: linked parameter incorrectly reset to fixed on form creation

refs #571

src/app/components/param-link/param-link.component.ts

@@ -259,9 +259,11 @@ export class ParamLinkComponent implements OnChanges, Observer, OnDestroy {
     }
 
     public updateParamList() {
+        let noMoreTarget = false;
         // liste des paramètres liables
         if (this.param.valueMode === ParamValueMode.LINK) {
             this._linkableParams = this.formService.getLinkableValues(this.param);
+            noMoreTarget = this._linkableParams.length === 0;
         } else {
             this._linkableParams = [];
         }
@@ -286,8 +288,10 @@ export class ParamLinkComponent implements OnChanges, Observer, OnDestroy {
             }
         } else {
             this._currentIndex = -1;
-            // back to SINGLE mode by default
-            this.param.valueMode = ParamValueMode.SINGLE;
+            // back to SINGLE mode by default if no more target module available
+            if (noMoreTarget) {
+                this.param.valueMode = ParamValueMode.SINGLE;
+            }
         }
     }