Don't throw error upon readding existing contracts (drizzle reinit)

src/Drizzle.js

@@ -81,12 +81,6 @@ class Drizzle {
       events
     )
 
-    if (this.contracts[drizzleContract.contractName]) {
-      throw new Error(
-        `Contract already exists: ${drizzleContract.contractName}`
-      )
-    }
-
     this.store.dispatch({ type: ContractActions.CONTRACT_INITIALIZING, contractConfig })
 
     this.contracts[drizzleContract.contractName] = drizzleContract