Clarify assertion for the sake of static analysis

Signed-off-by: Larry Gritz <[email protected]>

src/oiiotool/printinfo.cpp

@@ -529,9 +529,9 @@ OiioTool::print_info(std::ostream& out, Oiiotool& ot, ImageRec* img,
     }
 
     for (int s = 0, nsubimages = img->subimages(); s < nsubimages; ++s) {
-        DASSERT((opt.native ? img->nativespec(s) : img->spec(s)) != nullptr);
-        print_info_subimage(out, ot, s, nsubimages, img->miplevels(s),
-                            opt.native ? *img->nativespec(s) : *img->spec(s),
+        const ImageSpec* spec = opt.native ? img->nativespec(s) : img->spec(s);
+        DASSERT(spec != nullptr);
+        print_info_subimage(out, ot, s, nsubimages, img->miplevels(s), *spec,
                             img, nullptr, "", opt, field_re, field_exclude_re,
                             serformat, verbose);
         // If opt.subimages is not set, we print info about first subimage