wxGUI: fix histogram of imagery group on Windows, see https://trac.osgeo.org/grass/ticket/2961 (merge from trunk, https://trac.osgeo.org/grass/changeset/68238)

git-svn-id: https://svn.osgeo.org/grass/grass/branches/releasebranch_7_0@68239 15284696-431f-4ddb-bdfa-cd5b030d7da7

gui/wxpython/wxplot/dialogs.py

@@ -491,7 +491,7 @@ class HistRasterDialog(wx.Dialog):
         ret = grass.read_command('i.group', 
                                   group = '%s' % self.group, 
                                   quiet = True,
-                                  flags = 'g').strip().split('\n')
+                                  flags = 'g').strip().splitlines()
 
         if ret not in [None, '', ['']]:
             self.rasterList = ret