MDL-63658 core_favourites: fix errors discovered on oracle db

- Assuming 1 would be a record that didn't exist. should be using 0.
- Missing space before AND in sql in provider.

favourites/classes/privacy/provider.php

@@ -87,7 +87,7 @@ class provider implements \core_privacy\local\metadata\provider, \core_privacy\l
                  WHERE userid = :userid
                    AND component = :component";
         if (!is_null($itemtype)) {
-            $sql .= "AND itemtype = :itemtype";
+            $sql .= " AND itemtype = :itemtype";
         }
         $params = ['userid' => $userid, 'component' => $component, 'itemtype' => $itemtype];
         $contextlist->add_from_sql($sql, $params);

favourites/tests/repository_test.php

@@ -201,7 +201,7 @@ class favourite_repository_testcase extends advanced_testcase {
         // Try to get a favourite we know doesn't exist.
         // We expect an exception in this case.
         $this->expectException(dml_exception::class);
-        $favouritesrepo->find(1);
+        $favouritesrepo->find(0);
     }
 
     /**
@@ -414,7 +414,7 @@ class favourite_repository_testcase extends advanced_testcase {
         $this->assertTrue($favouritesrepo->exists($createdfavourite->id));
 
         // Verify exists returns false for non-existent favourite.
-        $this->assertFalse($favouritesrepo->exists(1));
+        $this->assertFalse($favouritesrepo->exists(0));
     }
 
     /**