Stop lookup error on none in project tree meta panel

nw/gui/itemdetails.py

@@ -227,13 +227,16 @@ class GuiItemDetails(QWidget):
     def updateViewBox(self, tHandle):
         """Populate the details box from a given handle.
         """
-        self.theHandle = tHandle
+        if tHandle is None:
-        nwItem = self.theProject.projTree[tHandle]
+            self.clearDetails()
+            return
 
+        nwItem = self.theProject.projTree[tHandle]
         if nwItem is None:
             self.clearDetails()
+            return
 
-        else:
+        self.theHandle = tHandle
         theLabel = nwItem.itemName
         if len(theLabel) > 100:
             theLabel = theLabel[:96].rstrip()+" ..."