Create detail view for part stock

- Shows all in-stock stock items

lib/inventree/part.dart

@@ -147,10 +147,38 @@ class InvenTreePart extends InvenTreeModel {
     };
   }
 
+  // Cached list of stock items
+  List<InvenTreeStockItem> stockItems = List<InvenTreeStockItem>();
+
+  int get stockItemCount => stockItems.length;
+
+  // Request stock items for this part
+  Future<void> getStockItems(BuildContext context, {bool showDialog=false}) async {
+
+    InvenTreeStockItem().list(
+      context,
+      filters: {
+        "part": "${pk}",
+        "in_stock": "true",
+      },
+      dialog: showDialog,
+    ).then((var items) {
+      stockItems.clear();
+
+      for (var item in items) {
+        if (item is InvenTreeStockItem) {
+          stockItems.add(item);
+        }
+      }
+    });
+  }
+
+  // Cached list of test templates
   List<InvenTreePartTestTemplate> testingTemplates = List<InvenTreePartTestTemplate>();
 
   int get testTemplateCount => testingTemplates.length;
 
+  // Request test templates from the serve
   Future<void> getTestTemplates(BuildContext context, {bool showDialog=false}) async {
 
     InvenTreePartTestTemplate().list(

lib/inventree/stock.dart

@@ -283,9 +283,9 @@ class InvenTreeStockItem extends InvenTreeModel {
   String get locationName {
     String loc = '';
 
-    if (jsondata.containsKey('location_detail')) {
-      loc = jsondata['location_detail']['name'] ?? '';
-    }
+    if (locationId == -1 || !jsondata.containsKey('location_detail')) return 'Unknown Location';
+
+    loc = jsondata['location_detail']['name'] ?? '';
 
     // Old-style name
     if (loc.isEmpty) {
@@ -298,11 +298,9 @@ class InvenTreeStockItem extends InvenTreeModel {
   String get locationPathString {
     String path = '';
 
-    if (jsondata.containsKey('location_detail')) {
-      path = jsondata['location_detail']['pathstring'] ?? '';
-    }
+    if (locationId == -1 || !jsondata.containsKey('location_detail')) return 'No location specified';
 
-    return path;
+    return jsondata['location_detail']['pathstring'] ?? '';
   }
 
   String get displayQuantity {