[LyX/master] Fix bug #10153: There's a mechanism in XHTML output that defers the output of tags until we know they're needed. In the case of HTML tables, empty cells should of course be output, so we need to force the tags to be output.

[Richard Heck]

commit 35d449c5dae11bbff53e2a35697a4fc3f03318ba
Author: Richard Heck <rgh...@lyx.org>
Date:   Mon Jun 20 10:21:22 2016 -0400

    Fix bug #10153: There's a mechanism in XHTML output that defers the
    output of tags until we know they're needed. In the case of HTML
    tables, empty cells should of course be output, so we need to force
    the tags to be output.

diff --git a/src/insets/InsetTabular.cpp b/src/insets/InsetTabular.cpp
index b5344df..7ad8663 100644
--- a/src/insets/InsetTabular.cpp
+++ b/src/insets/InsetTabular.cpp
@@ -3018,7 +3018,7 @@ docstring Tabular::xhtmlRow(XHTMLStream & xs, row_type 
row,
                else if (isMultiRow(cell))
                        attr << " rowspan='" << rowSpan(cell) << "'";
 
-               xs << html::StartTag(celltag, attr.str()) << html::CR();
+               xs << html::StartTag(celltag, attr.str(), true) << html::CR();
                ret += cellInset(cell)->xhtml(xs, runparams);
                xs << html::EndTag(celltag) << html::CR();
                ++cell;