Fix detection and drawing of whitespace-only changed blocks.

git-svn-id: http://tortoisesvn.googlecode.com/svn/trunk/src/TortoiseMerge@24100 4cfb86a4-2c7a-11df-bd14-c1e331e6ceac
Silence compiler warning.

git-svn-id: http://tortoisesvn.googlecode.com/svn/trunk/src/TortoiseMerge@24101 4cfb86a4-2c7a-11df-bd14-c1e331e6ceac