[flang] Don't attempt to compute element size if no DynamicType

[tskeith]

Summary

If an error has occurred a symbol may have a DeclTypeSpec but no
valid DynamicType. There is no need to compute the size of erroneous
symbols.

Also, we only need to process object entities and procedure entities.
All other kinds of symbols can be skipped.

This fixes another problem revealed by https://bugs.llvm.org/show_bug.cgi?id=47265

flang/lib/Semantics/compute-offsets.cpp

if (const DeclTypeSpec * type{object.symbol.GetType()}) {
       }
     }
     result += kind * (*object.substringStart - 1);
   }
   return result;
 }
 
 void ComputeOffsetsHelper::DoSymbol(Symbol &symbol) {
-  if (symbol.has<TypeParamDetails>() || symbol.has<SubprogramDetails>() ||
-      symbol.has<UseDetails>() || symbol.has<ProcBindingDetails>()) {
-    return; // these have type but no size
+  if (!symbol.has<ObjectEntityDetails>() && !symbol.has<ProcEntityDetails>()) {
+    return;
   }
   SizeAndAlignment s{GetSizeAndAlignment(symbol)};
   if (s.size == 0) {
     return;
   }
   offset_ = Align(offset_, s.alignment);
   symbol.set_size(s.size);
   symbol.set_offset(offset_);
auto ComputeOffsetsHelper::GetSizeAndAlignment(const Symbol &symbol)
   }
   result.size *= elements;
   return result;
 }
 
 auto ComputeOffsetsHelper::GetElementSize(const Symbol &symbol)
     -> SizeAndAlignment {
   const DeclTypeSpec *type{symbol.GetType()};
-  if (!type) {
+  if (!evaluate::DynamicType::From(type).has_value()) {
     return {};
   }
   // TODO: The size of procedure pointers is not yet known
   // and is independent of rank (and probably also the number
   // of length type parameters).
   if (IsDescriptor(symbol) || IsProcedurePointer(symbol)) {
     int lenParams{0};
     if (const DerivedTypeSpec * derived{type->AsDerived()}) {