Fix memory leak in xmlLoadEntityContent error path

Free the input stream if pushing it fails.

Found by OSS-Fuzz.

https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=43743

parser.c

@@ -8088,6 +8088,7 @@
      */
     if (xmlPushInput(ctxt, input) < 0) {
         xmlBufferFree(buf);
+	xmlFreeInputStream(input);
 	return(-1);
     }