manager: just warn about an invalid environment entry

Apart from bugs (as in #6152), this can happen if we ever make
our requirements for environment entries more stringent. As with
the rest of deserialization, we should just warn and continue.

src/basic/env-util.c

@@ -788,7 +788,7 @@ int serialize_environment(FILE *f, char **environment) {
 }
 
 int deserialize_environment(char ***environment, const char *line) {
-        char *uce = NULL;
+        char *uce;
         int r;
 
         assert(line);