refactor getLastCallChangeSince

libs/remix-debug/src/solidity-decoder/solidityProxy.js

@@ -97,9 +97,12 @@ class SolidityProxy {
     */
   extractStateVariablesAt (vmtraceIndex) {
     return new Promise((resolve, reject) => {
-      this.contractNameAt(vmtraceIndex).then((contractName) => {
-        resolve(this.extractStateVariables(contractName))
-      }).catch(reject)
+      this.contractNameAt(vmtraceIndex, (error, contractName) => {
+        if (error) {
+          return reject(error)
+        }
+        return resolve(this.extractStateVariables(contractName))
+      })
     })
   }