fix value=0 initialization for Gauge and Knob

Author: briandennis

src/components/Gauge.react.js

@@ -39,7 +39,7 @@ class Gauge extends React.Component {
 
     const colorValue = getColorValue(color);
 
-    const rawValue = this.props.value || min;
+    const rawValue = this.props.value != null ? this.props.value : min;
     const dirtyValue = logarithmic ? log.compute(rawValue) : rawValue;
     const value = sanitizeRangeValue({ min, max, value: dirtyValue });
 

src/components/Knob.react.js

@@ -28,7 +28,7 @@ class Knob extends Component {
     const currentDeg = valueToDeg({
       min: props.min,
       max: props.max,
-      value: props.value || props.min
+      value: props.value != null ? props.value : props.min
     });
 
     this.state = {