many: fix remaining check-pointer-deref issues

The updated parsing_hacks.h file uncovered a bunch of extra
things that the check-pointer-deref coccinelle script flags.

This commit fixes them to make the tree check-pointer-deref clean.

src/sysupdate/sysupdate-partition.c

@@ -158,6 +158,7 @@ int find_suitable_partition(
         int r;
 
         assert(device);
+        POINTER_MAY_BE_NULL(partition_type);
         assert(ret);
 
         r = fdisk_new_context_at(AT_FDCWD, device, /* read_only= */ true, /* sector_size= */ UINT32_MAX, &c);

src/sysupdate/sysupdate-resource.c

@@ -477,6 +477,7 @@ static int resource_load_from_web(
         int r;
 
         assert(rr);
+        POINTER_MAY_BE_NULL(web_cache);
 
         ci = web_cache ? web_cache_get_item(*web_cache, rr->path, verify) : NULL;
         if (ci) {

src/sysupdate/sysupdate-transfer.c

@@ -1009,6 +1009,7 @@ static int callout_context_new(const Transfer *t, const Instance *i, TransferPro
         assert(t);
         assert(i);
         assert(cb);
+        assert(ret);
 
         ctx = new(CalloutContext, 1);
         if (!ctx)