call cre.initCache() in CreDocument:engineInit()

frontend/document/credocument.lua

@@ -25,6 +25,9 @@ end
 
 function CreDocument:engineInit()
 	if not engine_initilized then
+		-- initialize cache
+		cre.initCache(1024*1024*64)
+		
 		-- we need to initialize the CRE font list
 		local fonts = Font:getFontList()
 		for _k, _v in ipairs(fonts) do