minor correction

kaleid/kernel/io/vga.c

@@ -47,7 +47,7 @@ error_t bvgaflusher(Buffer_t *buf)
     uchar *bufStart = (uchar *)lmax((size_t)buf->buf,
                             (size_t)currentLine
                             - (buf->nLines - 2 + bscroll) * buf->lineLen);
-    
+
     uchar *ptr = bufStart;
 
     // Writes the buffer's content
@@ -88,7 +88,7 @@ void IoScrollDown(void)
 void IoScrollUp(void)
 {
     // Keep the 8 below the 10 given to BOpenTermBufEx
-    if (bscroll < BtVideoInfo.framebufferHeight * 8)
+    if (bscroll < BtVideoInfo.framebufferHeight * 8 && bscroll < BStdOut->nLines)
         bscroll++;
     bvgaflusher(BStdOut);
 }