MimeData: Never detect anything as application/x-zerosize

- That mime type is pretty useless
- If there are two mime types that match a file by glob pattern, the mime
database implementation will find the best matching mime type by data of
*all* mime types and take that instead (this doesn't make sense btw).
That means that if .h is matched by c-hdr and c++-hdr, empty .h files are
detected as mime type application/x-zerosize, which is pretty useless

Change-Id: I4f9d532ef1efd29df00279c693486c92611485a8
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@theqtcompany.com>
Reviewed-by: Christian Kandeler <christian.kandeler@theqtcompany.com>
Reviewed-by: Daniel Teske <daniel.teske@theqtcompany.com>

src/libs/utils/mimetypes/mimedatabase.cpp

@@ -135,10 +135,10 @@ static inline bool isTextFile(const QByteArray &data)
 
 MimeType MimeDatabasePrivate::findByData(const QByteArray &data, int *accuracyPtr)
 {
-    if (data.isEmpty()) {
-        *accuracyPtr = 100;
-        return mimeTypeForName(QLatin1String("application/x-zerosize"));
-    }
+//    if (data.isEmpty()) {
+//        *accuracyPtr = 100;
+//        return mimeTypeForName(QLatin1String("application/x-zerosize"));
+//    }
 
     *accuracyPtr = 0;
     MimeType candidate = provider()->findByMagic(data, accuracyPtr);