rbutil: Properly initialize sansa / ipod bootloader buffer.

Fixes a crash on MacOS.

Change-Id: Ibb64a37266182c4ddfee32b2ac47b9d8f25a78e5

utils/rbutilqt/base/bootloaderinstallsansa.cpp

@@ -27,6 +27,7 @@
 BootloaderInstallSansa::BootloaderInstallSansa(QObject *parent)
         : BootloaderInstallBase(parent)
 {
+    sansa.sectorbuf = nullptr;
 }