if (!frame.isValid()) {  return; }
	private void analyzeIfNullBranch(Method method, IsNullValueDataflow invDataflow, BasicBlock basicBlock,		InstructionHandle lastHandle) throws DataflowAnalysisException {		IsNullValueFrame frame = invDataflow.getFactAtLocation(new Location(lastHandle, basicBlock));		IsNullValue top = frame.getTopValue();		// Find the line number.		int lineNumber = getLineNumber(method, lastHandle);		if (lineNumber < 0)			return;		boolean definitelySame = top.isDefinitelyNull();		boolean definitelyDifferent = top.isDefinitelyNotNull();		if (definitelySame || definitelyDifferent) {			if (definitelySame) {				if (DEBUG) System.out.println("Line " + lineNumber + " always same");				definitelySameBranchSet.set(lineNumber);			}			if (definitelyDifferent) {				if (DEBUG) System.out.println("Line " + lineNumber + " always different");				definitelyDifferentBranchSet.set(lineNumber);			}			//reportUselessControlFlow(classContext, method, lastHandle);		} else {			if (DEBUG) System.out.println("Line " + lineNumber + " undetermined");			undeterminedBranchSet.set(lineNumber);		}	}