Fix a possible refresh issue in the text boxes.

When delete_selection deletes text and insert char doesn't insert
anything the widget was not properly updated. The bug was mainly
theoretical in nature.

src/gui/widgets/text.cpp

@@ -132,12 +132,12 @@ void ttext_::insert_char(const Uint16 unicode)
 	delete_selection();
 
 	if(text_.insert_unicode(selection_start_, unicode)) {
-
-		// Update status
 		set_cursor(selection_start_ + 1, false);
-		update_canvas();
-		set_is_dirty(true);
 	}
+
+	// Since delete selection might have modified the content force an update.
+	update_canvas();
+	set_is_dirty(true);
 }
 
 void ttext_::copy_selection(const bool mouse)