shared: SandboxedProcessor: Fix scope issue with readablePathLocation

The pointer becomes invalid as readablePathLocation falls out of scope,
and exile.h quits with an error.

This may indicate exile API sucks, so something to think about there.

shared/sandboxedprocessor.cpp

@@ -35,9 +35,10 @@ void SandboxedProcessor::enableSandbox(QString readablePath)
 	}
 	policy->namespace_options = EXILE_UNSHARE_NETWORK | EXILE_UNSHARE_USER;
 
+	std::string readablePathLocation;
 	if(!readablePath.isEmpty())
 	{
-		std::string readablePathLocation = readablePath.toStdString();
+		readablePathLocation = readablePath.toStdString();
 		if(exile_append_path_policies(policy, EXILE_FS_ALLOW_ALL_READ, readablePathLocation.c_str()) != 0)
 		{
 			qCritical() << "Failed to add path policies";