Fix a panic in table-ops translation (#2350)

This fixes an issue where `ensure_inserted_block()` wasn't called before
we do some block manipulation in the Wasmtime translation of some
table-related instructions. It looks like `ensure_inserted_block()` is
otherwise called on most instructions being added, so we just need to
call it explicitly it seems here.

Closes #2347

tests/misc_testsuite/reference-types/no-panic.wast

@@ -0,0 +1,26 @@
+(module
+  (func $test (param i32) (result externref)
+        i32.const 0
+        if
+        else
+        end
+        local.get 0
+        table.get 0
+  )
+  (table 4 externref)
+  (export "test" (func $test))
+)
+
+(module
+  (func $test (param i32)
+        i32.const 0
+        if
+        else
+        end
+        local.get 0
+        ref.null extern
+        table.set 0
+  )
+  (table 4 externref)
+  (export "test" (func $test))
+)