Avoid NPE if buffer contains a null

Test: unit tests
Bug: None
Change-Id: Ibee4fdeadeb35547d6586015816afd7df53a7918
diff --git a/src/com/android/loganalysis/parser/LogcatParser.java b/src/com/android/loganalysis/parser/LogcatParser.java
index b32536d..366b851 100644
--- a/src/com/android/loganalysis/parser/LogcatParser.java
+++ b/src/com/android/loganalysis/parser/LogcatParser.java
@@ -192,6 +192,9 @@
     @Override
     public LogcatItem parse(List<String> lines) {
         for (String line : lines) {
+            if (line == null) {
+                continue;
+            }
             parseLine(line);
         }
         commit();