Don't crash on bad log path.

src/modules/umount/main.py

@@ -53,9 +53,10 @@ def run():
     log_destination = libcalamares.job.configuration["destLog"]
 
     # copy installation log before umount
-    if(os.path.exists('{!s}'.format(log_source))):
-        shutil.copy2('{!s}'.format(log_source), '{!s}/{!s}'.format(
-            root_mount_point, log_destination))
+    if(log_source)
+        if(os.path.exists('{!s}'.format(log_source))):
+            shutil.copy2('{!s}'.format(log_source), '{!s}/{!s}'.format(
+                root_mount_point, log_destination))
 
     if not root_mount_point:
         return ("No mount point for root partition in globalstorage",

src/modules/umount/umount.conf

@@ -1,6 +1,6 @@
 ---
-scrLog:       "/path/to/installation.log"
-destLog:      "/var/log/installation.log"
+#scrLog:       "/path/to/installation.log"
+#destLog:      "/var/log/installation.log"
 # example when using the Calamares created log:
 #srcLog:      "/root/.cache/Calamares/Calamares/Calamares.log"
 #destLog:     "/var/log/Calamares.log"