Fix krunner crash when open "/"

path.split may return empty string list if path contains only separator,
check the result before access it with last().

REVIEW: 126060
BUG: 355290
FIXED-IN: 5.5.0

runners/locations/locationrunner.cpp

@@ -135,6 +135,11 @@ static QString convertCaseInsensitivePath(const QString& path)
     // Split the string on /
     QStringList dirNames = path.split(QDir::separator(), QString::SkipEmptyParts);
 
+    // if split result is empty, path string can only contain separator.
+    if (dirNames.empty()) {
+        return QStringLiteral("/");
+    }
+
     // Match folders
     QDir dir(QStringLiteral("/"));
     for (int i = 0; i < dirNames.size() - 1; i++) {