do not move entire tab character down to next screen line

src/gui/BufferPane.cc

@@ -40,13 +40,13 @@ void BufferPane::walk_line(const Buffer::Iterator & start_of_line, std::function
         else
         {
             c_width = character_width(code_point);
-        }
             if (((screen_column + c_width) > m_columns) &&
                     (screen_column > 0))
             {
                 row_offset++;
                 screen_column = 0;
             }
+        }
         callback(row_offset, screen_column, virtual_column, c_width, i);
         virtual_column += c_width;
         if (code_point == '\t')