FileFilterHotspot: use QMimeDataBase::mimeTypeForFile()

It seems there is no way around checking for the extension then falling
back to letting QMimeDataBase examine the file contents; e.g. a file
named konsolerc, doesn't have an extension, but it is still a text file.

src/filterHotSpots/FileFilterHotspot.cpp

@@ -131,12 +131,10 @@ void FileFilterHotSpot::openWithEditorFromProfile(const QString &fullCmd, const
     // Here we are mostly interested in text-based files, e.g. if it's a
     // PDF we should let the system default app open it.
     QMimeDatabase mdb;
-    const auto mimeList = mdb.mimeTypesForFileName(path);
-    qCDebug(KonsoleDebug) << "FileFilterHotSpot: mime types for" << path << ":" << mimeList;
+    const auto mimeType = mdb.mimeTypeForFile(path);
+    qCDebug(KonsoleDebug) << "FileFilterHotSpot: mime type for" << path << ":" << mimeType;
 
-    // If mimeList is empty, then it's not a recognized mime type, e.g.
-    // a text file without an extension
-    if (mimeList.isEmpty() || !mimeList.at(0).inherits(QStringLiteral("text/plain"))) {
+    if (!mimeType.inherits(QStringLiteral("text/plain"))) {
         openWithSysDefaultApp(path);
         return;
     }