Fix NPE in Zipper-e pre-analysis

Reported-by: jpwang <jpwang@smail.nju.edu.cn>

Author: cs-cat

CHANGELOG.md

@@ -6,6 +6,9 @@
 - Pointer analysis
   - Add special handling for zero-length arrays to enhance PTA precision.
 
+### Fixes
+- Fix NPE in Zipper-e pre-analysis.
+
 ## [0.5.1] - 2024-12-31
 
 ### New Features

src/main/java/pascal/taie/analysis/pta/toolkit/zipper/Zipper.java

@@ -186,7 +186,10 @@ private Set<JMethod> getPrecisionCriticalMethods(PrecisionFlowGraph pfg) {
         if (isExpress) {
             int accPts = 0;
             for (JMethod m : pcms) {
-                accPts += methodPts.get(m).intValue();
+                MutableInt mPtsSize = methodPts.get(m);
+                if (mPtsSize != null) {
+                    accPts += mPtsSize.intValue();
+                }
             }
             if (accPts > pcmThreshold) {
                 // clear precision-critical method group whose accumulative