patch 8.0.0271: may get ml_get error when :tcldo deletes lines

Problem:    May get ml_get error when :tcldo deletes lines or switches to
            another buffer. (Nikolai Pavlov, closes #1421)
Solution:   Check the buffer and line every time.
diff --git a/src/testdir/Make_all.mak b/src/testdir/Make_all.mak
index bb646ee..c42aae6 100644
--- a/src/testdir/Make_all.mak
+++ b/src/testdir/Make_all.mak
@@ -193,6 +193,7 @@
 	    test_substitute.res \
 	    test_syntax.res \
 	    test_system.res \
+	    test_tcl.res \
 	    test_textobjects.res \
 	    test_undo.res \
 	    test_usercommands.res \