iOS app crashes consistently on iPad Pro when clicking "more" then "share" on another message in an encrypted room

Your application has presented a UIActivityViewController (). In its current trait environment, the modalPresentationStyle of a UIActivityViewController with this style is UIModalPresentationPopover. You must provide location information for this popover through the view controller's popoverPresentationController. You must provide either a sourceView and sourceRect or a barButtonItem. If this information is not known when you present the view controller, you may provide it in the UIPopoverPresentationControllerDelegate method -prepareForPopoverPresentation.
Application: Riot (im.vector.app)
Application version: 0.3.13 (r63)
Matrix SDK version: 0.7.11
Build: master #63
iPad 10.3.2

Main thread: YES
(
0 CoreFoundation 0x0000000188b3aff8 + 148
1 libobjc.A.dylib 0x000000018759c538 objc_exception_throw + 56
2 UIKit 0x000000018f6aaa60 + 2784
3 UIKit 0x000000018efb753c + 1972
4 UIKit 0x000000018efb526c + 452
5 UIKit 0x000000018eef1950 + 292
6 UIKit 0x000000018eee39ec + 528
7 UIKit 0x000000018ec57648 + 132
8 CoreFoundation 0x0000000188ae89a8 + 32
9 CoreFoundation 0x0000000188ae6630 + 372
10 CoreFoundation 0x0000000188ae6a7c + 956
11 CoreFoundation 0x0000000188a16da4 CFRunLoopRunSpecific + 424
12 GraphicsServices 0x000000018a480074 GSEventRunModal + 100
13 UIKit 0x000000018ecca058 UIApplicationMain + 208
14 Riot 0x00000001000a6d9c Riot + 257436
15 libdyld.dylib 0x0000000187a2559c + 4
)
2017-06-23 10:25:45.550 Riot[6496:5156988] *** Terminating app due to uncaught exception 'NSGenericException', reason: 'Your application has presented a UIActivityViewController (). In its current trait environment, the modalPresentationStyle of a UIActivityViewController with this style is UIModalPresentationPopover. You must provide location information for this popover through the view controller's popoverPresentationController. You must provide either a sourceView and sourceRect or a barButtonItem. If this information is not known when you present the view controller, you may provide it in the UIPopoverPresentationControllerDelegate method -prepareForPopoverPresentation.'

Reproduce the crash on an iPad by opening "more" and then "share" for another message in an encrypted room. Search the share flow for UIActivityViewController presentation and inspect its popoverPresentationController handling. Done means the share UI opens without the iPad popover exception.

Written by the indexing model from the issue text.