Correctly detect empty split lines at the end of tables

The previous detection was failing when some cells were empty (or fully
rendered) and when the current rendering position was not overflowing the page.
In this case, the line with empty cells was rendered and was visible for
example when cells had padding.

Author: liZe

tests/draw/test_table.py

@@ -1198,3 +1198,40 @@ def test_tables_20(assert_pixels):
       <col></col><col></col>
       <tbody><tr></tr><tr><td></td></tr></tbody>
       <tfoot></tfoot>''')
+
+
+@assert_no_logs
+def test_tables_21(assert_pixels):
+    assert_pixels('''
+      _________________________
+      _rrrrrrrrrrrrrrrrrrrrrrr_
+      _rBBBBBBBBBBrBBBBBBBBBBr_
+      _rBKKKKKKBBBrBKKKKKKBBBr_
+      _rBKKKKKKBBBrBKKKKKKBBBr_
+      _rBBBBBBBBBBrBBBBBBBBBBr_
+      _rrrrrrrrrrrrrrrrrrrrrrr_
+      _________________________
+      _________________________
+      _________________________
+      _________________________
+      _________________________
+      _rrrrrrrrrrrrrrrrrrrrrrr_
+      _rBBBBBBBBBBrBBBBBBBBBBr_
+      _rBKKKKKKBBBrBBBBBBBBBBr_
+      _rBKKKKKKBBBrBBBBBBBBBBr_
+      _rBBBBBBBBBBrBBBBBBBBBBr_
+      _rrrrrrrrrrrrrrrrrrrrrrr_
+      _________________________
+      _________________________
+      _________________________
+      _________________________
+    ''', '''
+      <style>
+        @font-face { src: url(weasyprint.otf); font-family: weasyprint }
+        @page { size: 25px 11px; margin: 1px }
+        table { border-collapse: collapse; font: 2px weasyprint; width: 100% }
+        td { background: blue; padding: 1px; border: 1px solid red }
+      </style>
+      <table>
+        <tr><td>abc</td><td>abc</td></tr>
+        <tr><td>abc</td><td></td></tr>''')

weasyprint/layout/table.py

@@ -272,17 +272,11 @@ def group_layout(group, position_y, bottom_space, page_is_empty,
             # Break if one cell was broken
             break_cell = False
             if resume_at:
-                values, = list(resume_at.values())
-                if len(row.children) == len(values):
-                    for cell_resume_at in values.values():
-                        if cell_resume_at != {0: None}:
-                            break_cell = True
-                            break
-                    else:
-                        # No cell was displayed, give up row
-                        next_position_y = inf
-                        page_is_empty = False
-                        resume_at = None
+                if all(child.empty for child in row.children):
+                    # No cell was displayed, give up row
+                    next_position_y = inf
+                    page_is_empty = False
+                    resume_at = None
                 else:
                     break_cell = True