document empty blocks in StashApplyCommandTest

Change-Id: I5b49bd00b00b86584b912fc5f503abf29db0f56e

org.eclipse.jgit.test/tst/org/eclipse/jgit/api/StashApplyCommandTest.java

 			git.stashApply().call();
 			fail("Exception not thrown");
 		} catch (StashApplyFailureException e) {
+			// expected
  		}
 		assertEquals("content3", read(PATH));
 	}
 			git.stashApply().call();
 			fail("Expected conflict");
 		} catch (StashApplyFailureException e) {
+			// expected
 		}
 		Status status = new StatusCommand(db).call();
 		assertEquals(1, status.getConflicting().size());
 			git.stashApply().call();
 			fail("Exception not thrown");
 		} catch (StashApplyFailureException e) {
+			// expected
 		}
 		assertEquals("content2", read(PATH));
 	}