mshtml/tests: Fix a memory leak (valgrind).

[Marvin]

Hi,

While running your changed tests on Windows, I think I found new failures.
Being a bot and all I'm not very good at pattern recognition, so I might be
wrong, but could you please double-check?
Full results can be found at
https://testbot.winehq.org/JobDetails.pl?Key=7746

Your paranoid android.


=== w2000pro (32 bit htmldoc) ===
htmldoc: unhandled exception c0000005 at 00090100

=== wxppro (32 bit htmldoc) ===
htmldoc: unhandled exception c0000005 at 3C8363A7

=== wvistau64 (32 bit htmldoc) ===
htmldoc: unhandled exception c0000005 at 00000000

=== w7u (32 bit htmldoc) ===
htmldoc.c:2863: Test failed: unexpected command 74
The test timed out

=== w8 (32 bit htmldoc) ===
htmldoc.c:2863: Test failed: unexpected command 74
htmldoc.c:2863: Test failed: unexpected command 74
htmldoc.c:2863: Test failed: unexpected command 74
htmldoc.c:6113: Test failed: LoadHistory failed: 80070057
htmldoc.c:6117: Test failed: expected FireBeforeNavigate2
htmldoc.c:6118: Test failed: expected Invoke_AMBIENT_SILENT
htmldoc.c:6119: Test failed: expected Invoke_AMBIENT_OFFLINEIFNOTCONNECTED
htmldoc.c:2781: Test failed: unexpected state L"uninitialized", expected 1
htmldoc.c:2781: Test failed: VT_I4(out)=0, expected 1
htmldoc.c:367: Test failed: expected Exec_SETTITLE
htmldoc.c:5666: Test failed: unexpected state L"uninitialized", expected 1
htmldoc.c:5666: Test failed: VT_I4(out)=0, expected 1
htmldoc.c:2781: Test failed: unexpected state L"uninitialized", expected 1
htmldoc.c:2781: Test failed: VT_I4(out)=0, expected 1
htmldoc.c:2781: Test failed: unexpected state L"uninitialized", expected 1
htmldoc.c:2781: Test failed: VT_I4(out)=0, expected 1
The test timed out

=== wvistau64 (64 bit htmldoc) ===
htmldoc: unhandled exception c0000005 at 000000007137D8A6