stats_engine: limit cycle surrounding lines

Change-Id: Iffb2d515101635cff5ee33949b704d51a1205d90

Author: BeYkeRYkt

src/stats_engine.py

@@ -176,7 +176,7 @@ def collect_stats(kernel_repo, cve_patch):
                     # check the surrounding lines
                     fp_above = []
                     idx = i - 1
-                    while len(fp_above) < len(above):
+                    while abs(idx) <= len(fp_contents) and len(fp_above) < len(above):
                         above_candidate = fp_contents[idx]
                         if above_candidate not in all_added:
                             fp_above.append(above_candidate)