Crash at runtime rather than panicking when if condition is erroneous

Closes #5318

crates/compiler/test_mono/generated/error_on_erroneous_condition.txt

@@ -0,0 +1,3 @@
+procedure Test.0 ():
+    let Test.2 : Str = "Erroneous: invalid condition type in if expression";
+    Crash Test.2

crates/compiler/test_mono/src/tests.rs

@@ -76,7 +76,7 @@ fn promote_expr_to_module(src: &str) -> String {
     buffer
 }
 
-fn compiles_to_ir(test_name: &str, src: &str, mode: &str, no_check: bool) {
+fn compiles_to_ir(test_name: &str, src: &str, mode: &str, allow_type_errors: bool, no_check: bool) {
     use roc_packaging::cache::RocCacheDir;
     use std::path::PathBuf;
 
@@ -146,7 +146,7 @@ fn compiles_to_ir(test_name: &str, src: &str, mode: &str, no_check: bool) {
         println!("Ignoring {} canonicalization problems", can_problems.len());
     }
 
-    assert!(type_problems.is_empty());
+    assert!(allow_type_errors || type_problems.is_empty());
 
     let main_fn_symbol = exposed_to_host.top_level_values.keys().copied().next();
 
@@ -2888,3 +2888,14 @@ fn layout_cache_structure_with_multiple_recursive_structures() {
         "#
     )
 }
+
+#[mono_test(allow_type_errors = "true")]
+fn error_on_erroneous_condition() {
+    indoc!(
+        r#"
+        app "test" provides [main] to "./platform"
+
+        main = if True then 1 else 2
+        "#
+    )
+}