fix failing test by defaulting to empty array

[JoviDeCroock]

No description provided.

[github-actions]

Size Change: +30 B (0%)

Total Size: 38.5 kB

Filename	Size	Change
dist/preact.js	3.74 kB	+7 B (0%)
dist/preact.min.js	3.74 kB	+7 B (0%)
dist/preact.module.js	3.76 kB	+6 B (0%)
dist/preact.umd.js	3.8 kB	+10 B (0%)

ℹ️ View Unchanged

Filename	Size	Change
compat/dist/compat.js	3 kB	0 B
compat/dist/compat.module.js	3.03 kB	0 B
compat/dist/compat.umd.js	3.05 kB	0 B
debug/dist/debug.js	3.08 kB	0 B
debug/dist/debug.module.js	3.07 kB	0 B
debug/dist/debug.umd.js	3.15 kB	0 B
devtools/dist/devtools.js	175 B	0 B
devtools/dist/devtools.module.js	185 B	0 B
devtools/dist/devtools.umd.js	252 B	0 B
hooks/dist/hooks.js	1.05 kB	0 B
hooks/dist/hooks.module.js	1.08 kB	0 B
hooks/dist/hooks.umd.js	1.13 kB	0 B
test-utils/dist/testUtils.js	390 B	0 B
test-utils/dist/testUtils.module.js	392 B	0 B
test-utils/dist/testUtils.umd.js	469 B	0 B

_{compressed-size-action}

[coveralls]

Coverage remained the same at 99.792% when pulling 1e8cbed on fix-test into e8a6b6d on fix/null-placeholder-sibling-placement.

[andrewiggins]

Just realized I messed up one of the tests in my branch. Rebase on top to see if everything still passes

[JoviDeCroock]

@andrewiggins I found another fix which works on the rebased branch

[JoviDeCroock]

There are scenario's where we skip an update with a placeholder, in this case tmp returns null with render, this is not an array so we [null] it