tilesdl.cc: fix segfault caused by negative Y-value

In my case, the cause was a crawlrc with these values:
  view_max_width=80
  view_max_height=70

I did a USE_TILE build, ran it, and the value of
crawl_view.msgsz.y became negative, causing a rather nasty
segfault later in initialization.

I'm pretty sure that using 'std::max' here is not the best
solution, but it at least avoids the negative number case.

Signed-off-by: Steven Noonan <steven@uplinklabs.net>

1 files changed, 1 insertions, 1 deletions

diff --git a/crawl-ref/source/tilesdl.cc b/crawl-ref/source/tilesdl.cc
index d9e3d26e4b..953c5ba563 100644
--- a/crawl-ref/source/tilesdl.cc
+++ b/crawl-ref/source/tilesdl.cc
@@ -1012,7 +1012,7 @@ void TilesFramework::do_layout()
     crawl_view.viewsz.y = Options.view_max_height;
     crawl_view.msgsz.x  = crt_width;
     // What *does* msgsz.y get set to? (jpeg)
-    crawl_view.msgsz.y  = crt_height - crawl_view.viewsz.y;
+    crawl_view.msgsz.y  = std::max(5, crt_height - crawl_view.viewsz.y);
 
     // Initial sizes.
     m_region_tile->dx = m_viewsc.x;