xfree86: Fix null pointer dereference

Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=93675
Signed-off-by: Kyle Guinn <elyk03@gmail.com>
[hdegoede@redhat.com: Simplify by adding 2 if conds together with &&]
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

hw/xfree86/i2c/xf86i2c.c

@@ -614,7 +614,7 @@ xf86CreateI2CDevRec(void)
 void
 xf86DestroyI2CDevRec(I2CDevPtr d, Bool unalloc)
 {
-    if (d) {
+    if (d && d->pI2CBus) {
         I2CDevPtr *p;
 
         /* Remove this from the list of active I2C devices. */
@@ -628,10 +628,10 @@ xf86DestroyI2CDevRec(I2CDevPtr d, Bool unalloc)
         xf86DrvMsg(d->pI2CBus->scrnIndex, X_INFO,
                    "I2C device \"%s:%s\" removed.\n",
                    d->pI2CBus->BusName, d->DevName);
-
-        if (unalloc)
-            free(d);
     }
+
+    if (unalloc)
+        free(d);
 }
 
 /* I2C transmissions are related to an I2CDevRec you must link to a