apps: convert ADVANCE to an expression

apps/shared/y4m.c:142:16: error: empty expression statement has no effect; remove unnecessary ';' to silence this warning [-Werror,-Wextra-semi-stmt]
    ADVANCE(10); // skip past header
               ^
apps/shared/y4m.c:183:23: error: empty expression statement has no effect; remove unnecessary ';' to silence this warning [-Werror,-Wextra-semi-stmt]
            ADVANCE(1);
                      ^
apps/shared/y4m.c:190:19: error: empty expression statement has no effect; remove unnecessary ';' to silence this warning [-Werror,-Wextra-semi-stmt]
        ADVANCE(1);
                  ^
apps/shared/y4m.c:197:15: error: empty expression statement has no effect; remove unnecessary ';' to silence this warning [-Werror,-Wextra-semi-stmt]
    ADVANCE(1); // advance past newline
              ^
apps/shared/y4m.c:212:19: error: empty expression statement has no effect; remove unnecessary ';' to silence this warning [-Werror,-Wextra-semi-stmt]
        ADVANCE(1);
                  ^
apps/shared/y4m.c:218:15: error: empty expression statement has no effect; remove unnecessary ';' to silence this warning [-Werror,-Wextra-semi-stmt]
    ADVANCE(1); // advance past newline
              ^
diff --git a/apps/shared/y4m.c b/apps/shared/y4m.c
index e326019..4c235e7 100644
--- a/apps/shared/y4m.c
+++ b/apps/shared/y4m.c
@@ -94,11 +94,11 @@
 }
 
 #define ADVANCE(BYTES)    \
-    {                     \
+    do {                  \
         p += BYTES;       \
         if (p >= end)     \
             goto cleanup; \
-    }
+    } while(0)
 
 avifBool y4mRead(avifImage * avif, const char * inputFilename)
 {