fix(PISystemInfo): correct guard for df output parsing

The guard ml.size_s() < 2 allowed size==2, but ml[2] was then
accessed — OOB read on truncated or unusual df output lines.

libs/main/system/pisysteminfo.cpp

@@ -177,7 +177,7 @@ PIVector<PISystemInfo::MountInfo> PISystemInfo::mountInfo(bool ignore_cache) {
 	l_df.pop_front();
 	for (const auto & s: l_df) {
 		PIStringList ml(s.replacedAll("  ", " ").split(" "));
-		if (ml.size_s() < 2) continue;
+		if (ml.size_s() < 3) continue;
 		if (ml.front() == "none") continue;
 		m.space_all   = ml[1].toULLong();
 		m.space_used  = ml[2].toULLong();