Verify input for getCellStyle function

partials/GridEditor.vue

@@ -1247,22 +1247,26 @@
         }
       },
       getCellStyle (obj) {
-        let x, y, w, h
+        if (!obj) return {}
+
+        let x = 0, y = 0, w = 0, h = 0
 
         // ----- existing cell
-        if (obj.id) {
+        if (obj.id && obj.target && obj.target.selector) {
           const parsed = obj.target.selector._value
-          x = parsed.xywh[0]
-          y = parsed.xywh[1]
-          w = parsed.xywh[2]
-          h = parsed.xywh[3]
+          if (Array.isArray(parsed.xywh) && parsed.xywh.length === 4) {
+            x = parsed.xywh[0]
+            y = parsed.xywh[1]
+            w = parsed.xywh[2]
+            h = parsed.xywh[3]
+          }
         }
         // ----- temp cell
         else {
-          x = obj.x
-          y = obj.y
-          w = obj.width
-          h = obj.height
+          x = obj.x || x
+          y = obj.y || y
+          w = obj.width || w
+          h = obj.height || h
         }
         return {
           'grid-column-start': x,