arc: Fix the crash by WindowPredictor

In some case, for example, window is defined as maximize or App
service not give a valid window info, window predictor will not
return a valid window bounds. It cause some follow up processing
crash since it assume the there is always a valid bounds.

BUG=b:259957098
TEST=ArcAppSingleRestoreHandlerTest.NullBoundsNotCauseCrash

Change-Id: I08f7921aedef814d72c3a6caa77888c1616d1e1a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4044947
Reviewed-by: Yuichiro Hanada <yhanada@chromium.org>
Commit-Queue: Shengsong Tan <sstan@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1075435}