NaN check and better init in lowpass

src/modules/controllib/blocks.cpp

@@ -121,6 +121,9 @@ int blockLimitSymTest()
 
 float BlockLowPass::update(float input)
 {
+	if (!isfinite(getState())) {
+		setState(input);
+	}
 	float b = 2 * float(M_PI) * getFCut() * getDt();
 	float a = b / (1 + b);
 	setState(a * input + (1 - a)*getState());

src/modules/controllib/blocks.hpp

@@ -114,7 +114,7 @@ public:
 // methods
 	BlockLowPass(SuperBlock *parent, const char *name) :
 		Block(parent, name),
-		_state(0),
+		_state(0.0f/0.0f /* initialize to invalid val, force into is_finite() check on first call */),
 		_fCut(this, "") // only one parameter, no need to name
 	{};
 	virtual ~BlockLowPass() {};