plug-ins: Fix ZDI-CAN-25100 for FLI plug-in

Resolves #13073
This patch adds a check to make sure we're not
writing beyond the bounds of the "pos" array.
This is the same check that we do earlier when
writing pos[xc++], but it was left off of the last
write command. Since "n" will be 0 if we get to the
end of the array, it prevents us from writing beyond
that.

plug-ins/file-fli/fli.c

@@ -1529,7 +1529,7 @@ fli_read_lc_2 (FILE          *f,
               xc += len << 1;
             }
         }
-      if (lpf)
+      if (lpf && xc < n)
         pos[xc] = lpn;
       yc++;
     }