fix segmentation fault in new assert (units without a faction)

conf/eressea.ini

@@ -1,3 +1,4 @@
+
 [eressea]
 base                           = .
 report                         = reports
@@ -6,13 +7,13 @@ lomem = 0
 debug                          = 0
 memcheck                       = 0
 locales                        = de,en
-;game_id = 0
 
 [lua]
 install                        = ../git
-paths = ../git/lunit:../git/scripts
+paths                          = lunit:scripts
 maxnmrs                        = 20
-rules = e2 ; can use -r to override
+rules                          = e2
 
 [editor]
 color                          = 1
+

src/kernel/unit.c

@@ -702,7 +702,7 @@ void set_level(unit * u, skill_t sk, int value)
 {
     skill *sv = u->skills;
 
-    assert(sk != SK_MAGIC || is_monsters(u->faction) || u->number == 1);
+    assert(sk != SK_MAGIC || !u->faction || is_monsters(u->faction) || u->number == 1);
     if (!skill_enabled(sk))
         return;