Fix a compile error since null propagating operator is not supported

NagaChiang · NagaChiang · commit 8767ca150bd0 · 2020-08-31T10:55:09.000+08:00
diff --git a/Assets/HTC.UnityPlugin/ViveInputUtility/Scripts/Misc/BasicGrabbable.cs b/Assets/HTC.UnityPlugin/ViveInputUtility/Scripts/Misc/BasicGrabbable.cs
@@ -281,7 +281,10 @@ public void OnColliderEventPressUp(ColliderButtonEventData eventData)
             	if (isGrabbed)
             	{
                 	caster.canGrab = true;
-                	m_onDrop?.Invoke(this);
+                    if (m_onDrop != null)
+                    {
+                        m_onDrop.Invoke(this);
+                    }
             	}
             	caster.canGrab = true;
         	}

Original file line number	Diff line number	Diff line change
`@@ -281,7 +281,10 @@ public void OnColliderEventPressUp(ColliderButtonEventData eventData)`
`281`	`281`	`if (isGrabbed)`
`282`	`282`	`{`
`283`	`283`	`caster.canGrab = true;`
`284`		`- m_onDrop?.Invoke(this);`
	`284`	`+ if (m_onDrop != null)`
	`285`	`+ {`
	`286`	`+ m_onDrop.Invoke(this);`
	`287`	`+ }`
`285`	`288`	`}`
`286`	`289`	`caster.canGrab = true;`
`287`	`290`	`}`