fix check for non-positive array size

Test/baseResults/negativeArraySize.comp.out

@@ -0,0 +1,24 @@
+negativeArraySize.comp
+Warning, version 310 is not yet complete; most version-specific features are present, but some are missing.
+ERROR: 0:9: '' : array size must be a positive integer 
+ERROR: 1 compilation errors.  No code generated.
+
+
+Shader version: 310
+local_size = (1, 1, 1)
+ERROR: node is still EOpNull!
+0:7  Function Definition: main( (global void)
+0:7    Function Parameters: 
+0:?   Linker Objects
+
+
+Linked compute stage:
+
+
+Shader version: 310
+local_size = (1, 1, 1)
+ERROR: node is still EOpNull!
+0:7  Function Definition: main( (global void)
+0:7    Function Parameters: 
+0:?   Linker Objects
+