public boolean isActive(BigInteger index) {
		if (indexMap == null) {
			return false;
		}
		return indexMap.getBlockInfo(index, fieldOffset) != null;
	}
Returns true if this FieldFactory will return a non-null value at the given line index. 
If the index is the first index for a block, then there may be non active fields at the 
beginning of the line. Similarly, the last line of a block may have inactive fields at 
the end of the line.

@param index the line index
@return true if this FieldFactory will produce a non-null value at the given line index.
Ghidra/Features/ByteViewer/src/main/java/ghidra/app/plugin/core/byteviewer/FieldFactory.java