Icon conversion: don't crash if source/destination paths have spaces (PR #736)

src/helpers/convertToIcns.js

@@ -27,7 +27,7 @@ function convertToIcns(pngSrc, icnsDest, callback) {
   }
 
   shell.exec(
-    `${PNG_TO_ICNS_BIN_PATH} ${pngSrc} ${icnsDest}`,
+    `"${PNG_TO_ICNS_BIN_PATH}" "${pngSrc}" "${icnsDest}"`,
     { silent: true },
     (exitCode, stdOut, stdError) => {
       if (stdOut.includes('icon.iconset:error') || exitCode) {

src/helpers/iconShellHelpers.js

@@ -28,7 +28,7 @@ function iconShellHelper(shellScriptPath, icoSrc, dest) {
     }
 
     shell.exec(
-      `${shellScriptPath} ${icoSrc} ${dest}`,
+      `"${shellScriptPath}" "${icoSrc}" "${dest}"`,
       { silent: true },
       (exitCode, stdOut, stdError) => {
         if (exitCode) {