GpuHost revised

modules/cloudsim/src/main/java/org/cloudbus/cloudsim/gpu/GpuHost.java

@@ -76,6 +76,15 @@ public class GpuHost extends Host {
 		}
 		// Checking GPU resources of the host
 		Vgpu vgpu = ((GpuVm) vm).getVgpu();
+		// if the VM has no vGPU -> return true.
+		if (vgpu == null) {
+			return true;
+		}
+		// if the VM has a vGPU and the host has no local video card -> return false.
+		else if(getVideoCardAllocationPolicy() == null) {
+			return false;
+		}
+		// if the VM has a vGPU and the host has video card(s) -> check compatibility.
 		return getVideoCardAllocationPolicy().isSuitable(vgpu);
 	}