[mlir] Fix possible null dereference during error logging in EmitC (#157456)

Fixes #157452

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 expects result type to be an "
+                       "lvalue type 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();

mlir/test/Dialect/EmitC/invalid_ops.mlir

@@ -532,6 +532,16 @@ func.func @use_global() {
 
 // -----
 
+emitc.global @myglobal_value : f32
+
+func.func @use_global() {
+  // expected-error @+1 {{'emitc.get_global' op on non-array type expects result type to be an lvalue type for the global @myglobal_value}}
+  %0 = emitc.get_global @myglobal_value : !emitc.array<2xf32>
+  return
+}
+
+// -----
+
 func.func @member(%arg0: !emitc.lvalue<i32>) {
   // expected-error @+1 {{'emitc.member' op operand #0 must be emitc.lvalue of EmitC opaque type values, but got '!emitc.lvalue<i32>'}}
   %0 = "emitc.member" (%arg0) {member = "a"} : (!emitc.lvalue<i32>) -> !emitc.lvalue<i32>