Crash when hitting room from unified search/browse directory

[jeangb]

To reproduce:

1. Open the unified search, Hit "Browse directory"
   or
2. Hit rooms tab, then the ROOM DIRECTORY seciton

Some rooms will provoque a crash when hitting them.
For example, "Linux" or "Unreal Engine" rooms.

[manuroe]

4744070372155289982 - 2017-06-22 08:00:39 +0000
*** setObjectForKey: key cannot be nil
Application: Riot (im.vector.app)
Application version: 0.4.0 (r0.4.0)
Matrix SDK version: 0.8.0
Build: develop #1959
iPhone 10.3.2

Main thread: YES
(
	0   CoreFoundation                      0x0000000184c1aff8 <redacted> + 148
	1   libobjc.A.dylib                     0x000000018367c538 objc_exception_throw + 56
	2   CoreFoundation                      0x0000000184afe528 <redacted> + 0
	3   Riot                                0x0000000100220008 Riot + 1998856 -> -[MXKRoomDataSourceManager addRoomDataSource:] (in Riot) (MXKRoomDataSourceManager.m:210)
	4   Riot                                0x000000010021ff84 Riot + 1998724 -> -[MXKRoomDataSourceManager roomDataSourceForRoom:create:] (in Riot) (MXKRoomDataSourceManager.m:203)
	5   Riot                                0x00000001000722b4 Riot + 238260 -> -[RoomViewController goBackToLive] (in Riot) (RoomViewController.m:3129)
	6   Riot                                0x000000010006f6a4 Riot + 226980 -> -[RoomViewController scrollViewDidScroll:] (in Riot) (RoomViewController.m:2613)
	7   UIKit                               0x000000018b05d8d4 <redacted> + 76
	8   UIKit                               0x000000018ad69c08 <redacted> + 436
	9   UIKit                               0x000000018ae20598 <redacted> + 272
	10  UIKit                               0x000000018ae0220c <redacted> + 388
	11  UIKit                               0x000000018ae01fac <redacted> + 516
	12  UIKit                               0x000000018ae028a0 <redacted> + 256
	13  UIKit                               0x000000018ae02744 <redacted> + 188
	14  UIKit                               0x000000018ad4907c <redacted> + 1200
	15  QuartzCore                          0x0000000187f39274 <redacted> + 148
	16  QuartzCore                          0x0000000187f2dde8 <redacted> + 292
	17  QuartzCore                          0x0000000187f2dca8 <redacted> + 32
	18  QuartzCore                          0x0000000187ea934c <redacted> + 252
	19  QuartzCore                          0x0000000187ed03ac <redacted> + 504
	20  UIKit                               0x000000018ad3e6c4 <redacted> + 256
	21  CoreFoundation                      0x0000000184bc89a8 <redacted> + 32
	22  CoreFoundation                      0x0000000184bc6630 <redacted> + 372
	23  CoreFoundation                      0x0000000184bc6a7c <redacted> + 956
	24  CoreFoundation                      0x0000000184af6da4 CFRunLoopRunSpecific + 424
	25  GraphicsServices                    0x0000000186560074 GSEventRunModal + 100
	26  UIKit                               0x000000018adb1058 UIApplicationMain + 208
	27  Riot                                0x0000000100079af0 Riot + 269040 -> main (in Riot) (main.m:30)
	28  libdyld.dylib                       0x0000000183b0559c <redacted> + 4
)

[jeangb]

Validated.