Theme code editor inserts multiple line breaks into code files

[bobsoap]

/wp-admin/theme-editor.php

When editing and saving a theme file, the editor adds empty an line after each line. This appears to happen on every save, and the empty lines keep adding up.

Code files shouldn't be altered in this manner. It changes the line numbers and messes everything up - a pain to debug.

[helenyhou]

#9716