Nesting string.splits in a for loop inner split gets NPE when assigned

So, today I hit a snag trying to split a string array element which has been split from a long string already.. It works like this: A string is created from a file. This string is split at blank lines (\n\n) which are basically paragraphs of text, which gets used as body text elsewhere. Each paragraph begins with a topic, followed by an asterisk, followed by the body text. Here's the issue - It would be too simple to, while iterating through each paragraph string element to split these at the asterisk character (escaped, of course). To demonstrate, the first part works well:

sections = formatted.split("\n\n");  //sections previously declared as string array
int lines = sections.length ;
for(int i= 0 ; i< lines; i++) {
    sections[i] = "Heading\n\n" + sections[i] ;

Now, when trying to perform another task in each iteration (yes, just join the two code windows together in your mind), it throws NPE on the second resulting index:

    String paragraph = sections[i];
    String[] half = paragraph.split("\\*");
    topics[i] = half[0];    //Topics also previously declared as array
}

The last line inside the iterator throws a NPE (not out of bounds). I can't tell if it's the I or the ) index.

I would really appreciate understanding why this doesn't work. Perhaps it's because I always seem to hit these problems well after midnight...

How can I build these two parallel instance arrays? Thanks!