REGRESSION(262547@main) ASSERTION FAILED: !m_size.isEmpty()

[obyknovenius]

533f864

REGRESSION(262547@main) ASSERTION FAILED: !m_size.isEmpty()
https://bugs.webkit.org/show_bug.cgi?id=255025

Reviewed by NOBODY (OOPS!).

We sometimes need to create an instance of `ShareableBitmapConfiguration`
with an empty size. For example, when we send a
`ShareableBitmapConfiguration` object in its initial state over IPC.

* Source/WebKit/Shared/ShareableBitmap.cpp:
(WebKit::ShareableBitmapConfiguration::ShareableBitmapConfiguration):

533f864

Misc	iOS, tvOS & watchOS	macOS	Linux	Windows
❌ 🧪 style	❌ 🛠 ios	❌ 🛠 mac	❌ 🛠 wpe	❌ 🛠 wincairo
	❌ 🛠 ios-sim	❌ 🛠 mac-AS-debug	❌ 🧪 wpe-wk2
❌ 🧪 webkitperl	❌ 🧪 ios-wk2	❌ 🧪 api-mac	❌ 🛠 gtk
	❌ 🧪 api-ios	❌ 🧪 mac-wk1	❌ 🧪 gtk-wk2
	❌ 🛠 tv	❌ 🧪 mac-wk2	❌ 🧪 api-gtk
	❌ 🛠 tv-sim	❌ 🧪 mac-AS-debug-wk2
	❌ 🛠 watch	❌ 🧪 mac-wk2-stress
	❌ 🛠 watch-sim

[webkit-early-warning-system]

EWS run on current version of this PR (hash 533f864)

Misc	iOS, tvOS & watchOS	macOS	Linux	Windows
❌ 🧪 style	❌ 🛠 ios	❌ 🛠 mac	❌ 🛠 wpe	❌ 🛠 wincairo
	❌ 🛠 ios-sim	❌ 🛠 mac-AS-debug	❌ 🧪 wpe-wk2
❌ 🧪 webkitperl	❌ 🧪 ios-wk2	❌ 🧪 api-mac	❌ 🛠 gtk
	❌ 🧪 api-ios	❌ 🧪 mac-wk1	❌ 🧪 gtk-wk2
	❌ 🛠 tv	❌ 🧪 mac-wk2	❌ 🧪 api-gtk
	❌ 🛠 tv-sim	❌ 🧪 mac-AS-debug-wk2
	❌ 🛠 watch	❌ 🧪 mac-wk2-stress
	❌ 🛠 watch-sim