Improve beam angle handling

* Limit beam angle to 120 degrees
* Limit (inner) beam cone radius to 0 (if outer radius is less than rim size)

src/pulsaranimationwidget.cpp

@@ -637,6 +637,7 @@ void PulsarAnimationWidget::setPulsarBeamAngle(const int degrees)
 {
     m_pulsarBeamOuterRadius = tan(deg2rad * degrees * 0.5f) * m_pulsarBeamLength;
     m_pulsarBeamInnerRadius = m_pulsarBeamOuterRadius - m_pulsarBeamRimSize;
+    if(m_pulsarBeamInnerRadius < 0.0) m_pulsarBeamInnerRadius = 0.0;
     updatePulseProfile();
 
     updateGL();

src/pulsatingscience.ui

@@ -245,7 +245,7 @@
           <string>Use this slider to adjust the pulsar beam spread angle (aperture or width)</string>
          </property>
          <property name="maximum">
-          <number>180</number>
+          <number>120</number>
          </property>
          <property name="pageStep">
           <number>5</number>