WeasyPrint: CSS Line Breaks/New Line doesn't work for non-latin chars

Hello.

The \A new line escape char in CSS raises AssesrtionError if the first char of the second line is non-latin, or in my case an Arabic letter. The following is what I get:

2019-03-18 15:33:39,460  [ERROR]  Error occured: Traceback (most recent call last):
  File "D:\my\project\pdf.py", line 126, in generate
    pdf = html.write_pdf(stylesheets=stylesheets)
  File "C:\Python37\lib\site-packages\weasyprint\__init__.py", line 198, in write_pdf
    font_config=font_config).write_pdf(
  File "C:\Python37\lib\site-packages\weasyprint\__init__.py", line 159, in render
    font_config)
  File "C:\Python37\lib\site-packages\weasyprint\document.py", line 361, in _render
    [Page(p, enable_hinting) for p in page_boxes],
  File "C:\Python37\lib\site-packages\weasyprint\document.py", line 361, in <listcomp>
    [Page(p, enable_hinting) for p in page_boxes],
  File "C:\Python37\lib\site-packages\weasyprint\layout\__init__.py", line 184, in layout_document
    make_margin_boxes(context, page, state))
  File "C:\Python37\lib\site-packages\weasyprint\layout\pages.py", line 435, in make_margin_boxes
    yield margin_box_content_layout(context, page, box)
  File "C:\Python37\lib\site-packages\weasyprint\layout\pages.py", line 444, in margin_box_content_layout
    absolute_boxes=[], fixed_boxes=[])
  File "C:\Python37\lib\site-packages\weasyprint\layout\blocks.py", line 363, in block_container_layout
    for line, resume_at in lines_iterator:
  File "C:\Python37\lib\site-packages\weasyprint\layout\inlines.py", line 56, in iter_line_boxes
    device_size, absolute_boxes, fixed_boxes, first_letter_style)
  File "C:\Python37\lib\site-packages\weasyprint\layout\inlines.py", line 105, in get_next_linebox
    waiting_floats, line_children=[])
  File "C:\Python37\lib\site-packages\weasyprint\layout\inlines.py", line 745, in split_inline_box
    line_placeholders, child_waiting_floats, line_children))
  File "C:\Python37\lib\site-packages\weasyprint\layout\inlines.py", line 583, in split_inline_level
    context, box, max_x - position_x, skip)
  File "C:\Python37\lib\site-packages\weasyprint\layout\inlines.py", line 1020, in split_text_box
    'Expected nothing or a preserved line break' % (between,))
AssertionError: Got '\n التاريخ: الأحد 3 مارس 2019' between two lines. Expected nothing or a preserved line break

I’m using:

WeasyPrint==45
cairocffi==1.0.2
CairoSVG==2.3.0

The part of CSS string causing the issue:

@top-right {{
				padding: 0.5cm;
				font-family: 'Dubai-Medium', sans-serif;
				content: " {doc_ref}: {ref} \A {doc_date}: {weekday} {day} {month} {year} \A {doc_addressee}: {addressee} ";
				display: block;
				white-space: pre;
				vertical-align: top;
			}}