As for such scenarios there is no thumb rule for it. But possibly we can follow to write the positive or most likely code in the if block and left out in the else block or default cases.

Should if/else statements be arranged by rareness of cases or difficulty of dealing with them?
I shot at a concert for the first time. The pictures were pretty good for the capability of my equipment, but on some shots, the light has a very strange flare. It isn't the usual rays, but some soft, non-symmetric form which I find quite strange, and, on most shots, distracting. 



On this image, you can see it just above Gino's head and also behind his back, to the right of the mic stand. I am not sure if the slight blue lines on the left side of the picture (they form a triangle aimed at Chris's head, maybe not visible on all monitors) are part of the problem or if they come from a different light source. 

What makes them appear, and how do I avoid them? 

I shot with a D90 with a 18-200 lens, no filters or hoods attached. The settings were quite strained (iso 3200, often at max length and max aperture for the length. This specific picture is 1/125, f 5.3, 95 mm). 
