checker: show error instead of panic, when using a `somemodule.NonExistingEnum.enum_value` (#13295)

vlib/v/checker/checker.v

@@ -3708,6 +3708,10 @@ pub fn (mut c Checker) enum_val(mut node ast.EnumVal) ast.Type {
 				c.error('unknown enum `$node.enum_name` (type_idx=0)', node.pos)
 				return ast.void_type
 			}
+		} else {
+			// if module prefix specified enum name given
+			c.error('unknown enum `$node.enum_name` (type_idx=0)', node.pos)
+			return ast.void_type
 		}
 	}
 	mut typ := ast.new_type(typ_idx)

vlib/v/checker/tests/enum_error_module.out

@@ -0,0 +1,7 @@
+vlib/v/checker/tests/enum_error_module.vv:5:13: error: unknown enum `missing_enum.ColoList` (type_idx=0)
+    3 | fn main() {
+    4 |     mut c := me.Color{
+    5 |         color: me.ColoList.black
+      |                   ~~~~~~~~~~~~~~
+    6 |     }
+    7 |     println(c)

vlib/v/checker/tests/enum_error_module.vv

@@ -0,0 +1,8 @@
+import missing_enum as me
+
+fn main() {
+	mut c := me.Color{
+		color: me.ColoList.black
+	}
+	println(c)
+}

vlib/v/checker/tests/modules/missing_enum.out

@@ -0,0 +1,5 @@
+vlib/v/checker/tests/modules/missing_enum/main.v:1:1: error: project must include a `main` module or be a shared library (compile with `v -shared`)
+    1 | module missing_enum
+      | ^
+    2 | 
+    3 | pub enum ColorList {

vlib/v/checker/tests/modules/missing_enum/main.v

@@ -0,0 +1,12 @@
+module missing_enum
+
+pub enum ColorList {
+	red
+	blue
+	green
+	black
+}
+
+pub struct Color {
+	color ColorList
+}