Only use RandomPalette if palette contains multiple materials.

src/test/java/RangeTest.java

@@ -1,4 +1,4 @@
-import com.dfsek.terra.Range;
+import org.polydev.gaea.math.Range;
 import org.junit.jupiter.api.Test;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertNull;