Offscreen, Linux. Fix native crash when OpenGL isn't available (#877)

Instead, fallback to Software.

Discovered during #876
investigation

## Explanation

We throw RenderException, and Fallback mechanism catches it and switches
to Software

## Testing

1. Setup the system without OpenGL
2. Run SkiaSwingLayer
3. See the native crash

skiko/src/awtMain/kotlin/org/jetbrains/skiko/swing/LinuxOpenGLSwingRedrawer.kt

@@ -15,7 +15,12 @@ internal class LinuxOpenGLSwingRedrawer(
 
     private val swingOffscreenDrawer = SwingOffscreenDrawer(swingLayerProperties)
 
-    private val offScreenContextPtr: Long = makeOffScreenContext()
+    private val offScreenContextPtr: Long = makeOffScreenContext().also {
+        if (it == 0L) {
+            throw RenderException("Cannot create OpenGL context")
+        }
+    }
+
 
     private var offScreenBufferPtr: Long = 0L