patch 9.0.1189: invalid memory access with folding and using "L"

Problem:    Invalid memory access with folding and using "L".
Solution:   Prevent the cursor from moving to line zero.
diff --git a/src/normal.c b/src/normal.c
index c319be5..3d9f74d 100644
--- a/src/normal.c
+++ b/src/normal.c
@@ -3729,7 +3729,8 @@
 		{
 		    (void)hasFolding(curwin->w_cursor.lnum,
 						&curwin->w_cursor.lnum, NULL);
-		    --curwin->w_cursor.lnum;
+		    if (curwin->w_cursor.lnum > curwin->w_topline)
+			--curwin->w_cursor.lnum;
 		}
 	    }
 	    else
diff --git a/src/testdir/test_fold.vim b/src/testdir/test_fold.vim
index adf9e52..f915a66 100644
--- a/src/testdir/test_fold.vim
+++ b/src/testdir/test_fold.vim
Binary files differ
diff --git a/src/version.c b/src/version.c
index 1d81e7b..64f7d88 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1189,
+/**/
     1188,
 /**/
     1187,