diff: fix NPE

this should not happen normally, but can be caused by other exceptions
IDEA-95430 IDEA-103824 diff: fix changed range calculation

bug case: modification right before previously deleted block

vcs version:
A
B
C

Before:
A
B

After:
X
B
diff: fix IDEA-97563 and related issues
diff: cleanup
added logging for BookmarkManagerTest#testBookmarkLineRemove
IDEA-126138 Open gradle test report should not be visible for non-gradle projects
EA-52085 (diagnostic performance impact eliminated)