Prevent crash when attempting to move marker on empty trace

Software/PC_Application/Traces/Marker/marker.cpp

@@ -1560,6 +1560,9 @@ bool Marker::isMovable()
         // helper traces are never movable by the user
         return false;
     }
+    if(trace()->size() == 0) {
+        return false;
+    }
     switch(type) {
     case Type::Manual:
     case Type::Delta:

Software/PC_Application/Traces/Math/tracemath.cpp

@@ -84,7 +84,14 @@ TraceMath::TypeInfo TraceMath::getInfo(TraceMath::Type type)
 
 TraceMath::Data TraceMath::getSample(unsigned int index)
 {
-    return data.at(index);
+    if(index < data.size()) {
+        return data[index];
+    } else {
+        TraceMath::Data d;
+        d.x = 0;
+        d.y = 0;
+        return d;
+    }
 }
 
 double TraceMath::getStepResponse(unsigned int index)