Fix some divide by 0 issues in Plasma Effect with single line buffers

xLights/effects/PlasmaEffect.cpp

@@ -100,7 +100,7 @@ void PlasmaEffect::Render(Effect *effect, const SettingsMap &SettingsMap, Render
 
     int block = buffer.BufferHt * buffer.BufferWi > 100 ? 1 : -1;
     parallel_for(0, buffer.BufferWi, [&] (int x) {
-        double rx = ((float)x / (buffer.BufferWi - 1)); // rx is now in the range 0.0 to 1.0
+        double rx = buffer.BufferWi <= 0 ? 0.0f : ((float)x / (buffer.BufferWi - 1)); // rx is now in the range 0.0 to 1.0
         double rx2 = rx * rx;
         double cx = rx + .5*sin_time_5;
         double cx2 = cx*cx;
@@ -113,7 +113,7 @@ void PlasmaEffect::Render(Effect *effect, const SettingsMap &SettingsMap, Render
         {
             // reference: http://www.bidouille.org/prog/plasma
 
-            double ry = ((float)y/(buffer.BufferHt-1)) ;
+            double ry = buffer.BufferHt <= 1 ? 0.0f : ((float)y/(buffer.BufferHt-1)) ;
             double v = v1;
 
             //  second equation

xLights/effects/metal/PlasmaFunctions.metal

@@ -35,15 +35,15 @@ uchar4 plasma_getMultiColorBlend(constant PlasmaData &data, half n, bool circula
 float plasmaCalc_vldpi(constant PlasmaData &data, uint32_t x, uint32_t y) {
     float time = data.time;
 
-    float rx = data.width > 0 ? ((float)x / (float)(data.width - 1)) : 0.0; // rx is now in the range 0.0 to 1.0
+    float rx = data.width > 1 ? ((float)x / (float)(data.width - 1)) : 0.0; // rx is now in the range 0.0 to 1.0
     float rx2 = rx * rx;
     float cx = rx + 0.5f * data.sin_time_5;
     float cx2 = cx*cx;
     float sin_rx_time = sin(rx + time);
 
     // 1st equation
     float v = sin(rx * 10.0f + time);
-    float ry = data.height > 0 ? ((float)y/(float)(data.height - 1)) : 0;
+    float ry = data.height > 1 ? ((float)y/(float)(data.height - 1)) : 0;
 
     //  second equation
     v += sin(10.0f*(rx*data.sin_time_2+ry*data.cos_time_3)+time);