do not move entire tab character down to next screen line

src/gui/BufferPane.cc

@@ -40,12 +40,12 @@ 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;
+            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;