private void tighten() {
		modificationNumber++;
		// tighten up
		nextIndex = 0;
		for (int i = 0; i < capacity; i++) {
			if (vertices[i] != null) {
				if (i > nextIndex) {
					vertices[nextIndex] = vertices[i];
					firstOutgoingEdge[nextIndex] = firstOutgoingEdge[i];
					firstIncomingEdge[nextIndex] = firstIncomingEdge[i];
					lastOutgoingEdge[nextIndex] = lastOutgoingEdge[i];
					lastIncomingEdge[nextIndex] = lastIncomingEdge[i];
					keyIndices.remove(vertices[i].key());
					keyIndices.put(vertices[i].key(), nextIndex);
					vertices[i] = null;
					firstOutgoingEdge[i] = null;
					firstIncomingEdge[i] = null;
					lastOutgoingEdge[i] = null;
					lastIncomingEdge[i] = null;
				}
				nextIndex++;
			}
		}
	}
Clean up the internal storage of the VertexSet.
Ghidra/Framework/Generic/src/main/java/ghidra/util/graph/VertexSet.java