@Override
		public boolean hasNext() {
			if (nextSymbol != null) {
				return true;
			}

			lock.acquire();
			try {
				while (nextSymbol == null && (forward ? it.hasNext() : it.hasPrevious())) {
					DBRecord rec = forward ? it.next() : it.previous();
					Symbol sym = getSymbol(rec);
					if (includeDefaultThunks || !isDefaultThunk(sym)) {
						nextSymbol = sym;
					}
				}
				return nextSymbol != null;
			}
			catch (IOException e) {
				program.dbError(e);
			}
			finally {
				lock.release();
			}
			return false;
		}
Called by the NamespaceManager when a namespace is removed; remove all symbols that have the
given namespace ID.

@param namespaceID ID of namespace being removed
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/database/symbol/SymbolManager.java