Alternate way of solving our uneven problem to work on JRuby

Works on all the rubies, or let's see what our CI says :)
ref: jruby/jruby#6048

Author: PragTob

lib/simplecov/source_file.rb

@@ -162,12 +162,15 @@ def no_cov_chunks
     end
 
     def build_no_cov_chunks
-      no_cov_lines = src.map.with_index(1).select { |line, _index| LinesClassifier.no_cov_line?(line) }
+      no_cov_lines = src.map.with_index(1).select { |line_src, _index| LinesClassifier.no_cov_line?(line_src) }
 
-      no_cov_lines.each_slice(2).map do |(_line_start, index_start), (_line_end, index_end)|
-        # if we have an uneven number of nocovs we assume they go to the
-        # end of the file
-        index_end ||= src.size
+      # if we have an uneven number of nocovs we assume they go to the
+      # end of the file, the source doesn't really matter
+      # Can't deal with this within the each_slice due to differing
+      # behavior in JRuby: jruby/jruby#6048
+      no_cov_lines << ["", src.size] if no_cov_lines.size.odd?
+
+      no_cov_lines.each_slice(2).map do |(_line_src_start, index_start), (_line_src_end, index_end)|
         index_start..index_end
       end
     end