fix(compiler): handle negative length in codeframe repeat

Author: yyx990803

Diff for: src/compiler/codeframe.js

@@ -38,11 +38,13 @@ export function generateCodeFrame (
 
 function repeat (str, n) {
   let result = ''
-  while (true) { // eslint-disable-line
-    if (n & 1) result += str
-    n >>>= 1
-    if (n <= 0) break
-    str += str
+  if (n > 0) {
+    while (true) { // eslint-disable-line
+      if (n & 1) result += str
+      n >>>= 1
+      if (n <= 0) break
+      str += str
+    }
   }
   return result
 }