CodeBlock getBlockAt(Address addr){
        Object[] blocks = getObjects(addr);
        for (int i=0; i < blocks.length; i++) {
            CodeBlock block = (CodeBlock) blocks[i];
            Address startAddr = block.getFirstStartAddress();
            if (startAddr.equals(addr)) {
                return block;
            }
        }
        return null;
    }
Get the cached block whose first entry-point is addr. 
This method is slightly more efficient than getBlockWithEntryAt,
however, it should only be used when the cached block has exactly
one entry-point.
@return the block with an entry-point address of addr, or null of
the block was not found.
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/block/CodeBlockCache.java