private PlaceholderVirtualBaseTableEntry existing(int tableIndex) throws PdbException {
		PlaceholderVirtualBaseTableEntry entry = entry(tableIndex);
		if (entry == null) {
			throw new PdbException(
				"No entry in Virtual Base Table for table index: " + tableIndex);
		}
		return entry;
	}
Constructor
@param owner the class that owns the table
@param parentage the parentage of the base class(es) of the table
Ghidra/Features/PDB/src/main/java/ghidra/app/util/pdb/classtype/PlaceholderVirtualBaseTable.java