[Cashtab] Patch addr validation error not displaying DestinationAddressMulti

Summary: Related to T2811. Increased height of DestinationAddressMultiCtn & ExpandingAddressInputCtn, padding over send button has been reduced as the taller ExpandingAddressInputCtn was pushing send button below the visible portion of the screen on smaller devices.

Test Plan:
cd web/cashtab && npm start
navigate to send screen
toggle the multiple recipients switch
input an incorrect eCash address
observe that the 'Invalid XEC address: someString' error appears
remove the incorrect eCash address
observe that the 'Input must not be blank' error appears

Reviewers: bytesofman, #bitcoin_abc, emack

Reviewed By: bytesofman, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D12738