Fix infinite loop when reading invalid ODS files

According to the spec, http://docs.oasis-open.org/office/v1.2/os/OpenDocument-v1.2-os-part1.html#__RefHeading__1415588_253892949,
a `<table:table-row>` can only ever contains a `<table:table-cell>` or
a `<table:covered-table-cell>`, but it seems that some invalid files in the wild
may contains something else. That would trigger an infinite loop. So instead we
totally ignore the invalid content.

Closes #832

CHANGELOG.md

@@ -24,6 +24,7 @@ and this project adheres to [Semantic Versioning](https://semver.org).
 - Improved performance when loading large spreadsheets - [#825](https://github.com/PHPOffice/PhpSpreadsheet/pull/825)
 - Improved performance when loading large spreadsheets - [#824](https://github.com/PHPOffice/PhpSpreadsheet/pull/824)
 - Fix color from CSS when reading from HTML - [#831](https://github.com/PHPOffice/PhpSpreadsheet/pull/831) 
+- Fix infinite loop when reading invalid ODS files - [#832](https://github.com/PHPOffice/PhpSpreadsheet/pull/832) 
 
 ## [1.5.2] - 2018-11-25
 

src/PhpSpreadsheet/Reader/Ods.php

@@ -210,6 +210,8 @@ public function listWorksheetInfo($pFilename)
                                     $mergeSize = $xml->getAttribute('table:number-columns-repeated');
                                     $currCells += (int) $mergeSize;
                                     $xml->read();
+                                } else {
+                                    $xml->read();
                                 }
                             } while ($xml->name != 'table:table-row');
                         }