Add test if import and migrate script exist

run.sh

@@ -3,20 +3,24 @@
 # First run the import program. It will read the db.dir from the config file in order to
 # find an old v1.json. This will be converted to the new db format.
 
+if [ -x ./bin/import ]; then
     ./bin/import
     if [ $? -ne 0 ]; then
         exit 1
     fi
+fi
 
 # Run the FFmpeg migration program. In case a FFmpeg 5 binary is present, it will create a
 # backup of the current DB and modify the FFmpeg parameter such that they are compatible
 # with FFmpeg 5.
 
+if [ -x ./bin/ffmigrate ]; then
     ./bin/ffmigrate
     if [ $? -ne 0 ]; then
         exit 1
     fi
+fi
 
 # Now run the core with the possibly converted configuration.
 
-./bin/core
+exec ./bin/core