Check mmap() return against correct value

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libswscale/utils.c

@@ -919,7 +919,11 @@ int sws_init_context(SwsContext *c, SwsFilter *srcFilter, SwsFilter *dstFilter)
             c->chrMmx2FilterCode = av_malloc(c->chrMmx2FilterCodeSize);
 #endif
 
+#ifdef MAP_ANONYMOUS
+            if (c->lumMmx2FilterCode == MAP_FAILED || c->chrMmx2FilterCode == MAP_FAILED)
+#else
             if (!c->lumMmx2FilterCode || !c->chrMmx2FilterCode)
+#endif
                 return AVERROR(ENOMEM);
             FF_ALLOCZ_OR_GOTO(c, c->hLumFilter   , (dstW        /8+8)*sizeof(int16_t), fail);
             FF_ALLOCZ_OR_GOTO(c, c->hChrFilter   , (c->chrDstW  /4+8)*sizeof(int16_t), fail);