Fix display when balance is zero.
Fix display when balance is zero.

If balance is zero (as with a fresh wallet), the display formatting is
broken due to an uninitialized value causing the home screen to not
load properly.

Closes #152

oktapodia/decrediton-appveyor-test,decred/decrediton,oktapodia/decrediton-appveyor-test,decred/decrediton,decred/decrediton,decred/decrediton,oktapodia/decrediton-appveyor-test,decred/decrediton,oktapodia/decrediton-appveyor-test,decred/decrediton,oktapodia/decrediton-appveyor-test