loader: Fix static analysis warnings

Handle possible null pointer dereferences.
Misc other warnings, nothing too serious.
Not addressing alloca concerns yet.

Change-Id: I712a6b4996a4d900604867e373521ff4d1c53df5
diff --git a/loader/extensions.c b/loader/extensions.c
index a57ab72..e135644 100644
--- a/loader/extensions.c
+++ b/loader/extensions.c
@@ -305,9 +305,10 @@
         loader_log(icd_term->this_instance, VK_DEBUG_REPORT_ERROR_BIT_EXT, 0,
                    "ICD associated with VkPhysicalDevice does not support "
                    "vkGetPhysicalDeviceGeneratedCommandsPropertiesNVX");
+    } else {
+        icd_term->GetPhysicalDeviceGeneratedCommandsPropertiesNVX(
+            phys_dev_term->phys_dev, pFeatures, pLimits);
     }
-    icd_term->GetPhysicalDeviceGeneratedCommandsPropertiesNVX(
-        phys_dev_term->phys_dev, pFeatures, pLimits);
 }
 
 // GPA helpers for non-KHR extensions