Fix NPEs in ClassWriter and variable merging

Author: jaskarth

src/org/jetbrains/java/decompiler/main/ClassWriter.java

@@ -1264,8 +1264,8 @@ else if (methodWrapper.varproc.getVarFinal(new VarVersionPair(index, 0)) == VarT
           throwsExceptions = true;
           buffer.append(" throws ");
 
-          boolean useDescriptor = hasDescriptor && !descriptor.exceptionTypes.isEmpty();
-          for (int i = 0; i < attr.getThrowsExceptions().size(); i++) {
+          boolean useDescriptor = descriptor != null && !descriptor.exceptionTypes.isEmpty();
+          for (int i = 0; i < (attr == null ? descriptor.exceptionTypes.size() : attr.getThrowsExceptions().size()); i++) {
             if (i > 0) {
               buffer.append(", ");
             }

src/org/jetbrains/java/decompiler/modules/decompiler/vars/VarDefinitionHelper.java

@@ -664,7 +664,7 @@ else if (obj instanceof Exprent) {
           VarType t1 = this.varproc.getVarType(ret.getKey());
           VarType t2 = this.varproc.getVarType(ret.getValue());
 
-          if (t1.isSuperset(t2) || t2.isSuperset(t1)) {
+          if (t1 != null && t2 != null && (t1.isSuperset(t2) || t2.isSuperset(t1))) {
             // TODO: this only checks for totally disjoint types, there are instances where merging is incorrect with primitives
 
             boolean ok = true;