PostgreSQL avoid duplicate category 1

https://github.com/FreshRSS/FreshRSS/issues/1312

app/SQL/install.sql.pgsql.php

@@ -51,7 +51,7 @@ $SQL_CREATE_TABLES = array(
 'CREATE INDEX %1$sis_read_index ON "%1$sentry" ("is_read");',
 'CREATE INDEX %1$sentry_lastSeen_index ON "%1$sentry" ("lastSeen");',
 
-'INSERT INTO "%1$scategory" (id, name) VALUES(1, \'%2$s\');',
+'INSERT INTO "%1$scategory" (id, name) SELECT 1, \'%2$s\' WHERE NOT EXISTS (SELECT id FROM "%1$scategory" WHERE id = 1);',
 'INSERT INTO "%1$sfeed" (url, category, name, website, description, ttl) VALUES(\'http://freshrss.org/feeds/all.atom.xml\', 1, \'FreshRSS.org\', \'http://freshrss.org/\', \'FreshRSS, a free, self-hostable aggregator…\', 86400);',
 'INSERT INTO "%1$sfeed" (url, category, name, website, description, ttl) VALUES(\'https://github.com/FreshRSS/FreshRSS/releases.atom\', 1, \'FreshRSS @ GitHub\', \'https://github.com/FreshRSS/FreshRSS/\', \'FreshRSS releases @ GitHub\', 86400);',
 );