Fix XLSX reading when shared strings is missing the uniqueCount attribute (#255)

Use "count" attribute as a fallback

tests/Spout/Reader/XLSX/ReaderTest.php

@@ -112,6 +112,20 @@ class ReaderTest extends \PHPUnit_Framework_TestCase
         $this->assertEquals($expectedRows, $allRows);
     }
 
+    /**
+     * @return void
+     */
+    public function testReadShouldSupportSheetWithSharedStringsMissingUniqueCountAttribute()
+    {
+        $allRows = $this->getAllRowsForFile('one_sheet_with_shared_strings_missing_unique_count.xlsx');
+
+        $expectedRows = [
+            ['s1--A1', 's1--B1'],
+            ['s1--A2', 's1--B2'],
+        ];
+        $this->assertEquals($expectedRows, $allRows);
+    }
+
     /**
      * @return void
      */