force at least 1hz cutoff in svfilter so it doesn't bias

notes

@@ -41,7 +41,7 @@ TODO {
     }
     
     filter cutoff preset for knobgadget
-    force at least 1hz in svfilter for normalization
+    - force at least 1hz in svfilter for normalization
     
     revert-to-saved menu action
     

xybrid/nodelib/svfilter.cpp

@@ -9,6 +9,7 @@ using namespace Xybrid::Audio;
 
 void SVFilter::process(AudioFrame in, double freq, double res, int ovs) {
     if (ovs <= 0) return;
+    freq = std::max(freq, 1.0);
     res = std::max(res, 0.01);
 
     double f = 2.0 * std::sin(PI * freq / (audioEngine->curSampleRate() * ovs));