BLACKLIST file allows for invalid syntax

BLACKLIST functionanilty described in: https://code.qt.io/cgit/qt/qtbase.git/tree/src/testlib/qtestblacklist.cpp

The documentation specifies a way to blacklisted whole testcase by listing platforms at the beginning of the file - see line 70: "Ungrouped lines at the beginning of a file apply to the whole testcase."
I have found this blacklist file:

[]
rhel
centos
ubuntu-18.04
ubuntu-20.04
[customGesture]

see more at::
https://code.qt.io/cgit/qt/qtbase.git/tree/tests/auto/other/gestures/BLACKLIST
Luckily [] are treated as 'applies to whole testcase' - but this functionality is not documented and most likely not intended.

more over - the [] OBSCURES and OVERWRITES properly blacklisted test functions eg:

[graphicsItemTreeGesture]
ubuntu-18.04
ubuntu-20.04

this function should be blaclisted only on ubuntu, but due to [] it is also blacklisted on rhel (check grafana for evidence)
I add link, but might be invalid by the time sb works on this bug:
https://testresults.qt.io/coin/logview/qt/qtbase/65ef2faa23680653814a55807f33dfe8462ced38/LinuxRHEL_8_4x86_64LinuxRHEL_8_4x86_64GCCqtci-linux-RHEL-8.4-x86_64-50-2f5ba9Sccache/f2bbd2bf030d47339234f38abcd0f3a68d3e6a54/test_1649237028