[BUG] possible crash in 'show table' on stats socket

Patch d5b9fd95 was missing an initialisation of "ctx.table.target", which caused
"show table" to segfault if it was issued after a "show errors" (target pointer == -1).
diff --git a/src/dumpstats.c b/src/dumpstats.c
index 9c89226..a3dc52e 100644
--- a/src/dumpstats.c
+++ b/src/dumpstats.c
@@ -617,6 +617,7 @@
 {
 	si->applet.ctx.table.data_type = -1;
 	si->applet.state = STAT_ST_INIT;
+	si->applet.ctx.table.target = NULL;
 	si->applet.ctx.table.proxy = NULL;
 	si->applet.ctx.table.entry = NULL;
 	if (show)