private void upgradeOldFallThroughMaps(TaskMonitor monitor)
			throws CancelledException, IOException {
		try {

			LongPropertyMapDB oldFallFroms = new LongPropertyMapDB(dbHandle, OpenMode.UPGRADE, this,
				null, addrMap, "FallFroms", monitor);

			LongPropertyMapDB oldFallThroughs = new LongPropertyMapDB(dbHandle, OpenMode.UPGRADE,
				this, null, addrMap, "FallThroughs", monitor);

			int cnt = oldFallThroughs.getSize();
			if (cnt != 0) {

				monitor.setMessage("Upgrade Fallthrough Overrides...");
				monitor.initialize(cnt);
				cnt = 0;

				AddressIterator addrIter = oldFallThroughs.getPropertyIterator();
				while (addrIter.hasNext()) {
					monitor.checkCancelled();
					Address addr = addrIter.next();

					Instruction instr = getInstructionAt(addr);
					if (instr == null) {
						continue;
					}

					try {
						long offset = oldFallThroughs.getLong(addr);
						Address toAddr = addr.getNewAddress(offset);
						instr.setFallThrough(toAddr);
					}
					catch (NoValueException e) {
						// skip
					}
					monitor.setProgress(++cnt);
				}
			}
			oldFallThroughs.delete();
			oldFallFroms.delete();

		}
		catch (VersionException e) {
			// Unexpected
			throw new IOException(e.getMessage());
		}
	}
Check for old fall-through/fall-from property maps.  These maps were never fully supported 
so we do not support the read-only mode, however we will support an upgrade of this data 
which is now stored as FALL_THROUGH References.
@param handle handle to database
@param openMode either READ_ONLY, UPDATE, or UPGRADE
@param monitor the task monitor use while upgrading.
@throws VersionException if the database is incompatible with the current schema
@throws IOException if a database io error occurs
@throws CancelledException if the user cancels the upgrade operation
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/database/code/CodeManager.java