msi: Fix parsing of an empty property followed by a non-empty property.

dlls/msi/action.c

@@ -231,6 +231,7 @@ static int parse_prop( const WCHAR *str, WCHAR *value, int *quotes )
                 if (!count) goto done;
                 in_quotes = 1;
                 ignore = 1;
+                len++;
                 break;
             case '"':
                 state = state_quote;
@@ -258,6 +259,7 @@ static int parse_prop( const WCHAR *str, WCHAR *value, int *quotes )
                 state = state_whitespace;
                 if (!count) goto done;
                 in_quotes = 1;
+                len++;
                 break;
             default:
                 if (!count) in_quotes = 0;
@@ -276,8 +278,9 @@ static int parse_prop( const WCHAR *str, WCHAR *value, int *quotes )
                 break;
             case ' ':
                 state = state_whitespace;
-                if (!count) goto done;
+                if (!count || (count > 1 && !len)) goto done;
                 in_quotes = 1;
+                len++;
                 break;
             default:
                 state = state_token;

dlls/msi/tests/install.c

@@ -6346,6 +6346,10 @@ static void test_command_line_parsing(void)
     r = MsiInstallProductA(msifile, cmd);
     ok(r == ERROR_SUCCESS, "Expected ERROR_SUCCESS, got %u\n", r);
 
+    cmd = "Q=\"\" P=\"one\"";
+    r = MsiInstallProductA(msifile, cmd);
+    ok(r == ERROR_INSTALL_FAILURE, "Expected ERROR_INSTALL_FAILURE, got %u\n", r);
+
     DeleteFile(msifile);
     RemoveDirectory("msitest");
 }