WOFF2: avoid a Msan error use-of-uninitialized-value in woff2_dec.cc

third_party/woff2/src/woff2_dec.cc

Index: third_party/woff2/src/woff2_dec.cc
diff --git a/third_party/woff2/src/woff2_dec.cc b/third_party/woff2/src/woff2_dec.cc
index 837eede131807f51dd7ae2e131b06fc4ec7a5761..ea1f1693bc5198507bfc5fa0ed89eb550d08f6b8 100644
--- a/third_party/woff2/src/woff2_dec.cc
+++ b/third_party/woff2/src/woff2_dec.cc
@@ -603,13 +603,12 @@ bool ReconstructGlyf(const uint8_t* data, Table* glyf_table,
     *glyf_checksum += ComputeULongSum(glyph_buf.get(), glyph_size);
 
     // We may need x_min to reconstruct 'hmtx'
-    Buffer x_min_buf(glyph_buf.get() + 2, 2);
-    int16_t x_min;
-    if (PREDICT_FALSE(!x_min_buf.ReadS16(&x_min))) {
-      return FONT_COMPRESSION_FAILURE();
+    if (n_contours > 0) {
+      Buffer x_min_buf(glyph_buf.get() + 2, 2);
+      if (PREDICT_FALSE(!x_min_buf.ReadS16(&info->x_mins[i]))) {
+        return FONT_COMPRESSION_FAILURE();
+      }
     }
-
-    info->x_mins[i] = n_contours != 0 ? x_min : 0;
   }
 
   // glyf_table dst_offset was set by ReconstructFont