public void fallThroughChanged(Address fromAddr, Reference newFallThroughRef) {
		if (newFallThroughRef != null &&
			newFallThroughRef.getReferenceType() != RefType.FALL_THROUGH) {
			throw new IllegalArgumentException("invalid reftype");
		}
		lock.acquire();
		try {
			InstructionDB instr = getInstructionAt(addrMap.getKey(fromAddr, false));
			if (instr == null) {
				// Do not allow fallthrough ref without instruction
				if (newFallThroughRef != null) {
					refManager.delete(newFallThroughRef);
				}
				return;
			}
			instr.fallThroughChanged(newFallThroughRef);
		}
		finally {
			lock.release();
		}
	}
Callback from ReferenceManager when a new fall-through reference is set.
@param fromAddr fall-through from location
@param newFallThroughRef new fallthrough reference or null if removed
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/database/code/CodeManager.java