disableWriteAheadLogging() is API level 16.

The function disableWriteAheadLogging() is only documented on API level
16. Currently, this causes the app to crash on start up on some devices,
for instance on a Nexus One.
Fix NPE when getting text from clipboard.

The clipboard may return null if the clipboard contains something other
than text. This is documented in the API but that case was not
considered by the code.
Merge pull request #130 from flerda/v2.0.2-wal

disableWriteAheadLogging() is API level 16.