Code analyser tool runned against QT including HarfBuzz reveiled resource leak
::Lookup_ChainContextPos2
Fix proposal:

diff --git a/src/3rdparty/harfbuzz/src/harfbuzz-gpos.c b/src/3rdparty/harfbuzz/src/harfbuzz-gpos.c
index a216005..75e30ae 100644
--- a/src/3rdparty/harfbuzz/src/harfbuzz-gpos.c
+++ b/src/3rdparty/harfbuzz/src/harfbuzz-gpos.c
@@ -5172,8 +5172,11 @@ static HB_Error  Lookup_ChainContextPos2(
     return error;
   known_backtrack_classes = 0;
 
-  if (ccpf2->MaxInputLength < 1)
+  if (ccpf2->MaxInputLength < 1) 
+  {
+    FREE( backtrack_classes );
     return HB_Err_Not_Covered;
+  }
 
   if ( ALLOC_ARRAY( input_classes, ccpf2->MaxInputLength, HB_UShort ) )
     goto End3;