quick fix task end date can not be null + test data

src/main/java/ch/zhaw/gartenverwaltung/TaskFormularController.java

@@ -135,6 +135,7 @@ public class TaskFormularController implements Initializable {
         });
 
         button.disableProperty().bind(start_datePicker.valueProperty().isNull()
+                .or(end_datePicker.valueProperty().isNull())
                 .or(taskName_field.textProperty().isEmpty())
                 .or(description_area.textProperty().isEmpty()));
     }

src/main/java/ch/zhaw/gartenverwaltung/types/TaskTemplate.java

@@ -42,7 +42,7 @@ public class TaskTemplate {
     }
 
     public Task generateTask(LocalDate realStartDate, long cropId) {
-        LocalDate endDate = relativeEndDate != null ? realStartDate.plusDays(relativeEndDate) : null;
+        LocalDate endDate = relativeEndDate != null ? realStartDate.plusDays(relativeEndDate) : realStartDate.plusDays(0);
 
         if (interval == null) {
             this.interval = 0;

src/main/resources/ch/zhaw/gartenverwaltung/io/plantdb.json

@@ -245,5 +245,86 @@
         "measures": "less water"
       }
     ]
+  },
+  {
+    "id": 3,
+    "name": "Test Potato",
+    "description": "The potato is a tuber, round or oval, with small white roots called  'eyes', that are growth buds. The size varies depending on the variety; the colour of the skin can be white, yellow or even purple.",
+    "light": 6,
+    "spacing": "35",
+    "soil": "sandy",
+    "image": "potato.jpg",
+    "pests": [
+      {
+        "name": "Rot",
+        "description": "Rot, any of several plant diseases, caused by any of hundreds of species of soil-borne bacteria, fungi, and funguslike organisms (Oomycota). Rot diseases are characterized by plant decomposition and putrefaction. The decay may be hard, dry, spongy, watery, mushy, or slimy and may affect any plant part.",
+        "measures": "Less water."
+      }
+    ],
+    "lifecycle": [
+      {
+        "startDate": "12-01",
+        "endDate": "12-02",
+        "type": "SOW",
+        "zone": "ZONE_8A",
+        "group": 0,
+        "wateringCycle": {
+          "litersPerSqM": 0,
+          "interval": null,
+          "notes": []
+        },
+        "taskTemplates": [
+          {
+            "name": "Germinate",
+            "relativeStartDate": -3,
+            "relativeEndDate": 0,
+            "description": "Take an egg carton and fill it with soil. Put the seedling deep enough so its half covered with soil. Keep it in 10-15 * Celsius with lots of light.",
+            "interval": null
+          }
+        ]
+      },
+      {
+        "startDate": "12-03",
+        "endDate": "12-15",
+        "type": "PLANT",
+        "zone": "ZONE_8A",
+        "group": 0,
+        "wateringCycle": {
+          "litersPerSqM": 25,
+          "interval": 7,
+          "notes": []
+        },
+        "taskTemplates": [
+          {
+            "name": "hilling",
+            "relativeStartDate": 0,
+            "relativeEndDate": 10,
+            "description": "When the plants are 20 cm tall, begin hilling the potatoes by gently mounding the soil from the center of your rows around the stems of the plant. Mound up the soil around the plant until just the top few leaves show above the soil. Two weeks later, hill up the soil again when the plants grow another 20 cm.",
+            "interval": 3
+          }
+        ]
+      },
+      {
+        "startDate": "12-16",
+        "endDate": "12-18",
+        "type": "HARVEST",
+        "zone": "ZONE_8A",
+        "group": 0,
+        "wateringCycle": {
+          "litersPerSqM": 0,
+          "interval": null,
+          "notes": []
+        },
+        "taskTemplates": [
+          {
+            "name": "Harvest",
+            "relativeStartDate": 0,
+            "relativeEndDate": 4,
+            "description": "Once the foliage has wilted and dried completely, harvest on a dry day. Store in a dark and cool location.",
+            "interval": null
+          }
+        ]
+      }
+    ]
   }
 ]