Fix a couple of point cloud related problems

* crash that occurs when loading an empty dataset
* trying to access outside of range when sampling color or size values

include/openspace/data/dataloader.h

@@ -71,6 +71,8 @@ struct Dataset {
     /// the dataset
     float maxPositionComponent = 0.f;
 
+    bool isEmpty() const;
+
     int index(std::string_view variableName) const;
     bool normalizeVariable(std::string_view variableName);
     glm::vec2 findValueRange(int variableIndex) const;

modules/base/rendering/pointcloud/renderablepointcloud.cpp

@@ -1072,12 +1072,12 @@ std::vector<float> RenderablePointCloud::createDataSlice() {
         }
 
         // Colors
-        if (_hasColorMapFile) {
+        if (_hasColorMapFile && colorParamIndex > -1) {
             result.push_back(e.data[colorParamIndex]);
         }
 
         // Size data
-        if (_hasDatavarSize) {
+        if (_hasDatavarSize && sizeParamIndex > -1) {
             // @TODO: Consider more detailed control over the scaling. Currently the value
             // is multiplied with the value as is. Should have similar mapping properties
             // as the color mapping

src/data/dataloader.cpp

@@ -623,6 +623,10 @@ ColorMap loadFileWithCache(std::filesystem::path path)
 
 } // namespace color
 
+bool Dataset::isEmpty() const {
+    return variables.empty() || entries.empty();
+}
+
 int Dataset::index(std::string_view variableName) const {
     for (const Dataset::Variable& v : variables) {
         if (v.name == variableName) {

src/rendering/colormappingcomponent.cpp

@@ -428,6 +428,10 @@ glm::vec4 ColorMappingComponent::colorFromColorMap(float valueToColorFrom) const
 }
 
 void ColorMappingComponent::initializeParameterData(const dataloader::Dataset& dataset) {
+    if (dataset.isEmpty()) {
+        return;
+    }
+
     // Initialize empty ranges based on values in the dataset
     for (const properties::OptionProperty::Option& option : dataColumn.options()) {
         int optionIndex = option.value;