data_size fix

Issue appeared with introduction of HR buffered messages on latest Fenix watch. e.g. HR for swims.

Author: adriangibbons

src/phpFITFileAnalysis.php

@@ -1159,7 +1159,8 @@ private function readHeader()
         }
 
         if (strlen($this->file_contents) - $header_size - 2 !== $this->file_header['data_size']) {
-            throw new \Exception('phpFITFileAnalysis->readHeader(): file_header[\'data_size\'] does not seem correct!');
+            // Overwrite the data_size. Seems to be incorrect if there are buffered messages e.g. HR records.
+            $this->file_header['data_size'] = $this->file_header['crc'] - $header_size + 2;
         }
     }