applying col_style to a list of rows of unequal length can cause an error as there is no cell at the index.

for example, with a structure like this:
********
**
********
***

col_style 2, 1
would fail as the second row has no cell at index 2. 

Thanks Don!

https://github.com/randym/axlsx/issues/15

2 files changed, 8 insertions, 0 deletions

diff --git a/lib/axlsx/workbook/worksheet/worksheet.rb b/lib/axlsx/workbook/worksheet/worksheet.rb
index 41d0f841..8b0f8bfa 100644
--- a/lib/axlsx/workbook/worksheet/worksheet.rb
+++ b/lib/axlsx/workbook/worksheet/worksheet.rb
@@ -195,6 +195,7 @@ module Axlsx
       offset = options.delete(:row_offset) || 0
       @rows[(offset..-1)].each do |r| 
         cells = r.cells[index]
+        next unless cells
         if cells.is_a?(Array)
           cells.each { |c| c.style = style }
         else
diff --git a/test/workbook/worksheet/tc_worksheet.rb b/test/workbook/worksheet/tc_worksheet.rb
index 4722a999..24e26155 100644
--- a/test/workbook/worksheet/tc_worksheet.rb
+++ b/test/workbook/worksheet/tc_worksheet.rb
@@ -69,6 +69,13 @@ class TestWorksheet < Test::Unit::TestCase
     assert_equal(@ws.rows.first.cells[0].style, 0)
   end
 
+  def test_col_style_with_empty_column
+    @ws.add_row [1,2,3,4]
+    @ws.add_row [1]
+    @ws.add_row [1,2,3,4]
+    assert_nothing_raised {@ws.col_style(1, 1)}
+  end
+
   def test_cols
     @ws.add_row [1,2,3,4]
     @ws.add_row [1,2,3,4]