[FIX] compiler: dynamic value on inputs doesn't turn 0 into empty string

In #1161, we fixed blockdom treating 0 as falsy when patching a value,
which would result in an empty attribute. It turns out that there is
another place where we had the same fallback, which is when we compute a
dynamic attribute value, so while blockdom had the ability to set the
value to 0, when using a dynamic attribute value we would never give it
0 as a value. This commit changes the fallback strategy for dynamic
attribute values to be the same as the one in blockdom.

closes #1358

src/compiler/code_generator.ts

@@ -580,8 +580,8 @@ export class CodeGenerator {
         if (attrName && isProp(ast.tag, attrName)) {
           // we force a new string or new boolean to bypass the equality check in blockdom when patching same value
           if (attrName === "value") {
-            // When the expression is falsy, fall back to an empty string
-            expr = `new String((${expr}) || "")`;
+            // When the expression is falsy (except 0), fall back to an empty string
+            expr = `new String((${expr}) === 0 ? 0 : ((${expr}) || ""))`;
           } else {
             expr = `new Boolean(${expr})`;
           }