patch 9.0.0198: ml_get error when switching buffer in Visual mode

Problem:    ml_get error when switching buffer in Visual mode.
Solution:   End Visual mode when switching buffer. (closes #10902)
diff --git a/src/buffer.c b/src/buffer.c
index 108d596..669cfa9 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -1818,6 +1818,14 @@
     static void
 enter_buffer(buf_T *buf)
 {
+    // when closing the current buffer stop Visual mode
+    if (VIsual_active
+#if defined(EXITFREE)
+	    && !entered_free_all_mem
+#endif
+	    )
+	end_visual_mode();
+
     // Get the buffer in the current window.
     curwin->w_buffer = buf;
     curbuf = buf;