uxa: don't call composite routines with no buffer.

We can get a case with gnome-terminal + links, where we get two arrays
of glyphs all with 0 width and 0 heights in them. If this happens
we manage to get to this case without any buffer setup and segfault.

(cherry picked from commit 717c7492a0f6ba3fb3eabda33515881eef314155)

1 files changed, 9 insertions, 7 deletions

diff --git a/uxa/uxa-glyphs.c b/uxa/uxa-glyphs.c
index dc518568..dd26362e 100644
--- a/uxa/uxa-glyphs.c
+++ b/uxa/uxa-glyphs.c
@@ -858,13 +858,15 @@ uxa_glyphs (CARD8 	 op,
 	}
 	list++;
     }
-    
-    if (maskFormat)
-	uxa_glyphs_to_mask(pMask, &buffer);
-    else
-	uxa_glyphs_to_dst(op, pSrc, pDst, &buffer,
-		       xSrc, ySrc, xDst, yDst);
-    
+
+    if (buffer.count) {
+	if (maskFormat)
+	    uxa_glyphs_to_mask(pMask, &buffer);
+	else
+	    uxa_glyphs_to_dst(op, pSrc, pDst, &buffer,
+			      xSrc, ySrc, xDst, yDst);
+    }
+
     if (maskFormat)
     {
 	x = extents.x1;