correct error with new compilers cache property

Author: eggplantzzz

packages/compile-solidity/src/run.ts

@@ -246,7 +246,7 @@ async function invokeCompiler({ compilerInput, options, solc }): Promise<{
     parser: options.parser,
     events: options.events,
     solcConfig: options.compilers.solc,
-    cache: options.compilers.cache
+    cache: options.compilers.solc?.cache
   };
 
   // in the browser, compile in a worker and return the result

packages/config/src/configDefaults.ts

@@ -61,8 +61,8 @@ export const getInitialConfig = ({
       grep: null
     },
     compilers: {
-      cache: "fileSystem",
       solc: {
+        cache: "fileSystem",
         settings: {
           //Note: The default solc version is *not* set here!
           //It's set in compilerSupplier/index.js in compile-solidity