Resolve "Prébarrages : interdire de supprimer le dernier bassin"

Closes #582 (closed)

src/app/components/pb-schema/pb-schema.component.ts

@@ -435,6 +435,13 @@ export class PbSchemaComponent implements AfterViewInit, AfterContentInit, OnIni
     }
 
     public get enableRemoveButton() {
+        // do not allow to remove last basin
+        if (this._selectedItem instanceof PbBassin) {
+            if (this.predamService.bassins.length == 1) {
+                return false;
+            }
+        }
+
         if (this._selectedItem === this.predamService.upstreamBassin) {
             return false;
         }