FsckError: Use @Nullable as field annotation (before any modifier)

More consistent with general coding style.

Change-Id: Idd0695c63d0b4a17640460e8c388ce12e952879a
Signed-off-by: Ivan Frade <ifrade@google.com>

org.eclipse.jgit/src/org/eclipse/jgit/internal/fsck/FsckError.java

@@ -61,7 +61,8 @@ public class FsckError {
 
 		final int type;
 
-		final @Nullable ObjectChecker.ErrorType errorType;
+		@Nullable
+		final ObjectChecker.ErrorType errorType;
 
 		/**
 		 * @param id