usp10: Initialize the GSUB table before doing any contextual shaping.

dlls/usp10/shape.c

@@ -3387,6 +3387,9 @@ void SHAPE_CharGlyphProp(HDC hdc, ScriptCache *psc, SCRIPT_ANALYSIS *psa, const
 
 void SHAPE_ContextualShaping(HDC hdc, ScriptCache *psc, SCRIPT_ANALYSIS *psa, WCHAR* pwcChars, INT cChars, WORD* pwOutGlyphs, INT* pcGlyphs, INT cMaxGlyphs, WORD *pwLogClust)
 {
+    if (!psc->GSUB_Table)
+        psc->GSUB_Table = load_gsub_table(hdc);
+
     if (ShapingData[psa->eScript].contextProc)
         ShapingData[psa->eScript].contextProc(hdc, psc, psa, pwcChars, cChars, pwOutGlyphs, pcGlyphs, cMaxGlyphs, pwLogClust);
 }