[gzip] Handle inflate returning Z_NEED_DICT

When `inflate` returns `Z_NEED_DICT` this is currently not reported as
an error and callers may assume that the decompression succeeded when it
did not. In particular, a compressed table in a woff file may not
actually be decompressed and written as expected, leaving the backing
memory for the expanded table uninitialized.

* src/gzlip/ftgzip.c (FT_Gzip_Uncompress): treat `Z_NEED_DICT` as
indicating invalid data since there is no means to provide a dictionary.

Bug: https://bugs.chromium.org/p/chromium/issues/detail?id=1335712
diff --git a/src/gzip/ftgzip.c b/src/gzip/ftgzip.c
index 34bbe4d..915182e 100644
--- a/src/gzip/ftgzip.c
+++ b/src/gzip/ftgzip.c
@@ -790,6 +790,9 @@
     if ( err == Z_DATA_ERROR )
       return FT_THROW( Invalid_Table );
+    if ( err == Z_NEED_DICT )
+      return FT_THROW( Invalid_Table );
     return FT_Err_Ok;