fix: Fixes undefined error in some cases after patching config.js.

debian/jitsi-meet-web-config.postinst

@@ -176,6 +176,10 @@ case "$1" in
         fi
 
         # Fixes multi-stream flags to workaround problem with mobile joining a multi-stream call with multi-stream disabled
+        FIX_MSG="#Enables multi-stream, do not delete me"
+        if ! grep -q "^${FIX_MSG}" $JITSI_MEET_CONFIG; then
+            sed -i "s/config.flags.sourceNameSignaling/${FIX_MSG}\nconfig.flags = config.flags || {};\nconfig.flags.sourceNameSignaling/g" $JITSI_MEET_CONFIG
+        fi
         if ! grep -q "^config.flags.sourceNameSignaling*" $JITSI_MEET_CONFIG; then
             echo "config.flags.sourceNameSignaling = true;" >> $JITSI_MEET_CONFIG
         fi