gobj: Assert instead of crash when printing unresolved GV(A)D

panda/src/gobj/geomVertexArrayData.cxx

@@ -59,8 +59,10 @@ ALLOC_DELETED_CHAIN_DEF(GeomVertexArrayDataHandle);
  * file.
  */
 GeomVertexArrayData::
-GeomVertexArrayData() : SimpleLruPage(0) {
-  _contexts = nullptr;
+GeomVertexArrayData() :
+  SimpleLruPage(0),
+  _array_format(nullptr),
+  _contexts(nullptr) {
 
   // Can't put it in the LRU until it has been read in and made valid.
 }
@@ -180,7 +182,8 @@ set_usage_hint(GeomVertexArrayData::UsageHint usage_hint) {
  */
 void GeomVertexArrayData::
 output(std::ostream &out) const {
-  out << get_num_rows() << " rows: " << *get_array_format();
+  nassertv(_array_format != nullptr);
+  out << get_num_rows() << " rows: " << *_array_format;
 }
 
 /**
@@ -188,6 +191,7 @@ output(std::ostream &out) const {
  */
 void GeomVertexArrayData::
 write(std::ostream &out, int indent_level) const {
+  nassertv(_array_format != nullptr);
   _array_format->write_with_data(out, indent_level, this);
 }
 

panda/src/gobj/geomVertexData.I

@@ -582,6 +582,7 @@ CacheEntry(GeomVertexData *source, CacheKey &&key) noexcept :
  */
 INLINE GeomVertexData::CData::
 CData() :
+  _format(nullptr),
   _usage_hint(UH_unspecified)
 {
 }

panda/src/gobj/geomVertexData.cxx

@@ -1268,7 +1268,9 @@ output(ostream &out) const {
   if (!get_name().empty()) {
     out << get_name() << " ";
   }
-  out << get_num_rows() << " rows: " << *get_format();
+  const GeomVertexFormat *format = get_format();
+  nassertv(format != nullptr);
+  out << get_num_rows() << " rows: " << *format;
 }
 
 /**
@@ -1279,8 +1281,15 @@ write(ostream &out, int indent_level) const {
   if (!get_name().empty()) {
     indent(out, indent_level) << get_name() << "\n";
   }
-  get_format()->write_with_data(out, indent_level + 2, this);
-  CPT(TransformBlendTable) table = get_transform_blend_table();
+  CPT(TransformBlendTable) table;
+  const GeomVertexFormat *format = nullptr;
+  {
+    CDReader cdata(_cycler);
+    format = cdata->_format;
+    table = cdata->_transform_blend_table.get_read_pointer();
+  }
+  nassertv(format != nullptr);
+  format->write_with_data(out, indent_level + 2, this);
   if (table != nullptr) {
     indent(out, indent_level)
       << "Transform blend table:\n";