[FEATURE] Fix records references in EM update script

Enable the update script, which may be run in the
extension manager, to fix records with wrong
references (wrongly assigned »flux parent«) automatically.

Refs #1176

class.ext_update.php

@@ -6,24 +6,37 @@
  * Performs update tasks for extension flux
  */
  // @codingStandardsIgnoreStart
-class ext_update {
+class ext_update
+{
 
 	/**
 	 * @return boolean
 	 */
 	public function access() {
-		return TRUE;
+		return true;
 	}
 
 	/**
 	 * @return string
 	 */
 	public function main() {
-		$GLOBALS['TYPO3_DB']->exec_UPDATEquery('tt_content', 'colPos = -42', array('colPos' => 18181));
+		$content = '';
+
+		$GLOBALS['TYPO3_DB']->exec_UPDATEquery('tt_content', 'colPos = -42', ['colPos' => 18181]);
+		$content .= 'Switch to positive colPos (see #477): ' .
+			$GLOBALS['TYPO3_DB']->sql_affected_rows() . ' rows affected' . PHP_EOL;
+
+		// Fix records with wrong references (see #1176)
+		$GLOBALS['TYPO3_DB']->exec_UPDATEquery('tt_content', 'tx_flux_parent > 0 AND tx_flux_column = \'\'', ['tx_flux_parent' => 0]);
+		$content .= 'Fix records with wrong references (see #1176): ' .
+			$GLOBALS['TYPO3_DB']->sql_affected_rows() . ' rows affected' . PHP_EOL;
+
 		$GLOBALS['TYPO3_DB']->exec_TRUNCATEquery('cf_extbase_reflection');
 		$GLOBALS['TYPO3_DB']->exec_TRUNCATEquery('cf_extbase_reflection_tags');
 		$GLOBALS['TYPO3_DB']->exec_TRUNCATEquery('cf_extbase_object');
 		$GLOBALS['TYPO3_DB']->exec_TRUNCATEquery('cf_extbase_object_tags');
-		return $GLOBALS['TYPO3_DB']->sql_affected_rows() . ' rows have been updated. System object caches cleared.';
+		$content .= 'System object caches cleared.' . PHP_EOL;
+
+		return nl2br($content);
 	}
 }