Merge pull request #2 from CodeCox/fix-null-issue1

NoClear() Extension : fixes NPE Issue #1

orx-no-clear/src/main/kotlin/NoClear.kt

@@ -15,6 +15,7 @@ class NoClear : Extension {
 
 
     override fun beforeDraw(drawer: Drawer, program: Program) {
+        if (program.width > 0 && program.height > 0) {    // only if the window is not minimised
             if (renderTarget == null || renderTarget?.width != program.width || renderTarget?.height != program.height) {
                 renderTarget?.let {
                     it.colorBuffer(0).destroy()
@@ -32,6 +33,7 @@ class NoClear : Extension {
                     }
                 }
             }
+        }
         renderTarget?.bind()
     }