fix: handle null constructor in NewFilledInstanceInstruction and varargs with too few args

[chenjunwenhao]

Summary

Fix two runtime crashes that expose raw Java exceptions instead of meaningful QLExpress error messages.

Bug 1: NullPointerException in NewFilledInstanceInstruction

When using the classified-JSON syntax ({'@class': 'ClassName', ...}) to instantiate a class that has no no-arg constructor, loadConstructor() returns null but the code proceeds to call constructor.newInstance(), resulting in a raw NPE.

Fix: Added a null check matching the pattern already used in NewInstanceInstruction, reporting NO_SUITABLE_CONSTRUCTOR with a clear message.

Reproduction:

{'@class': 'com.example.ClassWithNoDefaultCtor', 'field': 'value'}

Bug 2: ArrayIndexOutOfBoundsException in MemberResolver.adapt2VarArgTypes()

When calling a varargs Java method with fewer arguments than the number of required (non-vararg) parameters, System.arraycopy copies more elements than the destination array can hold, causing an ArrayIndexOutOfBoundsException.

Fix: Added a pre-check in both resolveConstructor() and resolveMethod() to skip varargs candidates where argTypes.length < parameterTypes.length - 1, allowing the resolver to gracefully report "method not found" instead of crashing.

Reproduction:

// Java: static int sum(int required, int... rest)
VarArgsHelper.sum()  // 0 args for a method requiring at least 1

Additional: Preserve exception cause chains

The catch (Exception e) blocks in both NewFilledInstanceInstruction.newInstance() and NewInstanceInstruction.newObject() did not pass the caught exception to ErrorReporter.report(), losing the original stack trace. Now e is passed as the catchObj parameter, consistent with how InvocationTargetException is already handled in the same methods.

Test plan

• testNewFilledInstanceWithNoDefaultConstructor — verifies NO_SUITABLE_CONSTRUCTOR error instead of NPE
• testVarArgsMethodWithTooFewArgs — verifies graceful error for too-few-args varargs call, plus validates normal varargs calls (0 args, exact minimum, multiple varargs items) still work correctly