bug: after loading user defined channel the cross-section display is not updated unless you change the WSE

[AlisterH]

Hi, great plugin. I'm looking at some minor enhancements to it, but I've noticed a little bug:

• Start the plugin and go to User Defined Channel.
• Load a text file of station and elevation values.
• Notice that the cross-section display did not update. It should.
• Try changing the units, channel slope or roughness coefficient - the cross-section display will still not update.
• Resize the window and the cross-section display will be blanked.
• Change the WSE and the cross-section display will start updating correctly.

[AlisterH]

Another very minor one is that if you cancel the "Select tab or space delimited text file containing station and elevation data" dialog, you get an unnecessary Error dialog.