handle graph export with empty data (#239); closes #233

Co-authored-by: Dominik Demuth <dominik.demuth@physik.tu-darmstadt.de>
Reviewed-on: IPKM/nmreval#239

src/gui_qt/lib/pg_objects.py

@@ -183,6 +183,8 @@ class PlotItem(PlotDataItem):
             brush = self.opts['symbolBrush']
             if isinstance(brush, tuple):
                 self.opts['symbolcolor'] = brush
+            elif isinstance(brush, str):
+                self.opts['symbolcolor'] = int(f'0x{brush[1:3]}', 16), int(f'0x{brush[3:5]}', 16), int(f'0x{brush[5:7]}', 16)
             else:
                 c = brush.color()
                 self.opts['symbolcolor'] = c.red(), c.green(), c.blue()
@@ -340,7 +342,8 @@ class PlotItem(PlotDataItem):
 
         opts = self.opts
         item_dic = {
-            'x': x, 'y': y,
+            'x': x,
+            'y': y,
             'name': opts.get('name', ''),
             'symbolsize': opts['symbolSize'],
         }