Fix null pointer error in universequery logic

Author: tinder-maxwellelliott

src/main/java/com/bazel_diff/main.java

@@ -230,7 +230,7 @@ public Integer call() throws IOException {
         Boolean shouldHashAllSourceFiles = false;
         String universeQuery = "//...";
         if (exclusive != null) {
-            if (exclusive.hashAllSourcefiles) {
+            if (exclusive.hashAllSourcefiles != null) {
                 shouldHashAllSourceFiles = exclusive.hashAllSourcefiles;
             } else {
                 universeQuery = exclusive.universeRdepsQuery;