add some initial BufferView unit tests

src/core/BufferView.cc

@@ -43,6 +43,12 @@ void BufferView::iter_lines(
                 break;
         }
     }
+    else
+    {
+        m_cursor_screen_row = 0;
+        m_cursor_screen_column = 0;
+        m_cursor_virtual_column = 0;
+    }
 }
 
 /**************************************************************************