log: don't try to get the channel of a non-existing logger

Signed-off-by: Miklos Vajna <vmiklos@collabora.com>
Change-Id: Ic08043dac01b682184ff440b2f7d7f4f3df9522e

common/Log.cpp

@@ -382,6 +382,11 @@ namespace Log
 
     void setThreadLocalLogLevel(const std::string& logLevel)
     {
+        if (!Static.getLogger())
+        {
+            return;
+        }
+
         // Use the same channel for all Poco loggers.
         auto channel = Static.getLogger()->getChannel();