Steps to reproduce the issue:
1. Create a new project with default settings.
2. Try selecting different Editor's layouts ("Window->Layouts")
3. Notice that the Editor becomes grey after selecting these layouts:

"2 by 3"
"Tall"
"Wide"

4. Notice that these layouts work fine:

"4 Split"
"Default"

Reproduced only with 5.5.0a6.

Note1:
GIF attached.

Note2:
Reproduced on both Windows and OSX.

Note3:
With some machines the Editor crashed on:

#0  0x007fff930484e9 in objc_msgSend
#1  0x007fff9a25db35 in -[NSView _recursiveBreakKeyViewLoop]
#2  0x007fff8ea37d74 in CFArrayApplyFunction
#3  0x007fff9a25db35 in -[NSView _recursiveBreakKeyViewLoop]
#4  0x007fff8ea37d74 in CFArrayApplyFunction
#5  0x007fff9a25db35 in -[NSView _recursiveBreakKeyViewLoop]
#6  0x007fff9a25cf72 in -[NSWindow dealloc]
#7  0x007fff99fe4637 in -[NSWindow release]
#8  0x007fff9304db3b in (anonymous namespace)::AutoreleasePoolPage::pop(void*)
#9  0x007fff8ea33c12 in _CFAutoreleasePoolPop
#10 0x007fff96ea09ea in -[NSAutoreleasePool drain]