[mlir] Fix possible null dereference during error logging in Dialect/EmitC

Author: apach301

mlir/lib/Dialect/EmitC/IR/EmitC.cpp

@@ -1320,7 +1320,11 @@ GetGlobalOp::verifySymbolUses(SymbolTableCollection &symbolTable) {
 
   // global has non-array type
   auto lvalueType = dyn_cast<LValueType>(resultType);
-  if (!lvalueType || lvalueType.getValueType() != globalType)
+  if (!lvalueType)
+    return emitOpError("on non-array type result type is not defined "
+                       "for the global @")
+           << getName();
+  if (lvalueType.getValueType() != globalType)
     return emitOpError("on non-array type expects result inner type ")
            << lvalueType.getValueType() << " to match type " << globalType
            << " of the global @" << getName();